All Exams >
Grade 8 >
Science for Grade 8 >
All Questions
All questions of Simple Circuits for Grade 8 Exam
The magnetic field lines inside a long current-carrying solenoid are near-
- a)Straight
- b)Circular
- c)Elliptical
- d)Parabolic
Correct answer is option 'A'. Can you explain this answer?
The magnetic field lines inside a long current-carrying solenoid are near-
a)
Straight
b)
Circular
c)
Elliptical
d)
Parabolic
|
Gunjan Lakhani answered |
The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at all points inside the solenoid. That is, the field is uniform inside the solenoid.
Magnetic lines of force originate from the- a)North pole
- b)Center point
- c)South pole
- d)Either north pole or south pole
Correct answer is option 'A'. Can you explain this answer?
Magnetic lines of force originate from the
a)
North pole
b)
Center point
c)
South pole
d)
Either north pole or south pole
|
Ananya Das answered |
The direction of magnetic line of force is the direction of force on a North Pole, so the magnetic lines of force always begin on the North Pole of a magnet and end on the South Pole of the magnet. When a small magnetic compass is placed along a lie of force, it sets itself along the line tangential to it. Hence, the line drawn from the South Pole of the compass to its North pole shows the direction of the magnetic field.
An electric current flowing through a conductor produces
- a)Magnetic field
- b)Electric Field
- c)Electromagnetic field
- d)None of these
Correct answer is option 'A'. Can you explain this answer?
An electric current flowing through a conductor produces
a)
Magnetic field
b)
Electric Field
c)
Electromagnetic field
d)
None of these
|
Vikas Kumar answered |
An electric current through a metallic conductor produces a magnetic field around it.
A magnetic field existing around a magnet can be represented by magnetic field lines. Magnetic field lines always form:- a)open loops
- b)closed loops
- c)straight lines
- d)Both closed loops and straight lines
Correct answer is option 'B'. Can you explain this answer?
A magnetic field existing around a magnet can be represented by magnetic field lines. Magnetic field lines always form:
a)
open loops
b)
closed loops
c)
straight lines
d)
Both closed loops and straight lines
|
Krishna Iyer answered |
Magnetic field lines can never cross, meaning that the field is unique at any point in space. Magnetic field lines are continuous, forming closed loops without beginning or end.
Overloading is due to- a)Insulation of wire is damaged
- b)fault in the appliances
- c)accidental hike in supply voltage
- d)All of the above
Correct answer is option 'D'. Can you explain this answer?
Overloading is due to
a)
Insulation of wire is damaged
b)
fault in the appliances
c)
accidental hike in supply voltage
d)
All of the above
|
Rohit Sharma answered |
Overloading occurs when there is any fault in the appliances or the insulation of wire got damaged. It also occurs when there is sudden hike in supply voltage.
Which of the following metal is not attracted by a magnet?- a)Cobalt
- b)Nickel
- c)Steel
- d)Silver
Correct answer is option 'D'. Can you explain this answer?
Which of the following metal is not attracted by a magnet?
a)
Cobalt
b)
Nickel
c)
Steel
d)
Silver
|
|
Ananya Das answered |
In the natural states, metals such as brass, copper , gold and silver will not attract magnets. This is because they are weak metals to start with. Magnets only attach themselves to strong metals such as iron and cobalt and that is why not all types of metals can make magnets stick to them.
Can you explain the answer of this question below:A vertical wire carries a current straight down. To the east of this wire, the magnetic field points:
- A:
eastwards
- B:
downwards
- C:
southwards
- D:
northwards
The answer is c.
A vertical wire carries a current straight down. To the east of this wire, the magnetic field points:
eastwards
downwards
southwards
northwards
|
|
Anjana Khatri answered |
Use the right hand rule. Point your thumb down. Your fingers curl toward the south when you look on the east side of the wire.
Earth wire carries- a)current
- b)voltage
- c)no current
- d)heat
Correct answer is option 'C'. Can you explain this answer?
Earth wire carries
a)
current
b)
voltage
c)
no current
d)
heat
|
|
Kiran Mehta answered |
A "grounding" wire on the other hand is a safety wire that has intentionally been connected to earth. The grounding wire does not carry electricity under normal circuit operations. It's purpose is to carry electrical current only under short circuit or other conditions that would be potentially dangerous.
What should be the core of an electromagnet?- a)soft iron
- b)hard iron
- c)rusted iron
- d)none of above
Correct answer is option 'A'. Can you explain this answer?
What should be the core of an electromagnet?
a)
soft iron
b)
hard iron
c)
rusted iron
d)
none of above
|
Chetna bhatia answered |
The core of an electromagnet should be a) soft iron.
Explanation: Soft iron is used as the core of an electromagnet because of its high magnetic permeability, meaning it can easily magnetize and demagnetize in response to an external magnetic field. When an electric current is passed through a coil wrapped around the soft iron core, it becomes strongly magnetized and creates a strong magnetic field. When the current is removed, the magnetism of the soft iron core quickly disappears, allowing the electromagnet to be turned on and off easily. Hard iron, on the other hand, retains its magnetism longer and is not suitable for electromagnets that need to be switched on and off frequently. Rusted iron is not ideal because the rust would interfere with the magnetic properties and reduce the efficiency of the electromagnet.
Explanation: Soft iron is used as the core of an electromagnet because of its high magnetic permeability, meaning it can easily magnetize and demagnetize in response to an external magnetic field. When an electric current is passed through a coil wrapped around the soft iron core, it becomes strongly magnetized and creates a strong magnetic field. When the current is removed, the magnetism of the soft iron core quickly disappears, allowing the electromagnet to be turned on and off easily. Hard iron, on the other hand, retains its magnetism longer and is not suitable for electromagnets that need to be switched on and off frequently. Rusted iron is not ideal because the rust would interfere with the magnetic properties and reduce the efficiency of the electromagnet.
Current flowing in conductors A and B is same, what is the ratio of the magnetic field produced around the conductor A at a distance of 5 cm from the conductor to the magnetic field produced around the conductor B at a distance of 2 cm from this conductor is- a)0.04
- b)0.4
- c)4.0
- d)10
Correct answer is option 'B'. Can you explain this answer?
Current flowing in conductors A and B is same, what is the ratio of the magnetic field produced around the conductor A at a distance of 5 cm from the conductor to the magnetic field produced around the conductor B at a distance of 2 cm from this conductor is
a)
0.04
b)
0.4
c)
4.0
d)
10
|
Indu Gupta answered |
Magnetic field produced is directly proportional to the current flowing and inversely proportional to the distance from the conductor. Since current flowing in both conductors is same only distance matters here. Since field is inversely proportional to distance ;
B(A) / B(B) = d(B) / d ( A) = 0.2/0.5
=> 0.4
B(A) / B(B) = d(B) / d ( A) = 0.2/0.5
=> 0.4
Moving two like poles together usually causes a magnet resting on a table to repel and rotate. This occurs because:- a)Like magnetic poles repel
- b)Unlike magnetic poles attract
- c)Both of these
- d)None of these
Correct answer is option 'C'. Can you explain this answer?
Moving two like poles together usually causes a magnet resting on a table to repel and rotate. This occurs because:
a)
Like magnetic poles repel
b)
Unlike magnetic poles attract
c)
Both of these
d)
None of these
|
Ishan Choudhury answered |
Like poles of magnet repel each other and unlike poles of magnet attract each other.
In Fleming’s left-hand rule the thumb indicates the direction of- a)magnetic field applied
- b)current flown in the conductor
- c)induced current
- d)mechanical force on the conductor
Correct answer is option 'D'. Can you explain this answer?
In Fleming’s left-hand rule the thumb indicates the direction of
a)
magnetic field applied
b)
current flown in the conductor
c)
induced current
d)
mechanical force on the conductor
|
|
Krishna Iyer answered |
In Fleming’s left-hand rule the thumb indicates the direction of mechanical force acting on the conductor. The forefinger points in the direction of magnetic field and the central finger in the direction of current flowing in the conductor.
Which of the following properties of a proton can change while it moves freely in a magnetic field ?- a)Mass
- b)Speed
- c)Velocity
- d)Momentum
Correct answer is option 'C'. Can you explain this answer?
Which of the following properties of a proton can change while it moves freely in a magnetic field ?
a)
Mass
b)
Speed
c)
Velocity
d)
Momentum
|
|
Arun Sharma answered |
Each moving charged particle in a magnetic field experiences a force. The direction of force experienced by a positive charge is given by Fleming's left hand rule. The force acting on the proton would change both velocity and momentum.
Which of the following property of a proton can change while it moves freely in a magnetic field? (There maybe more then one correct answers)- a)Mass
- b)Speed
- c)Velocity
- d)Momentum.
Correct answer is option 'C'. Can you explain this answer?
Which of the following property of a proton can change while it moves freely in a magnetic field? (There may
be more then one correct answers)
a)
Mass
b)
Speed
c)
Velocity
d)
Momentum.
|
|
Anjana Khatri answered |
The correct options are (c) and (d). The magnetic force acts perpendicular to the direction of motion of the proton. It does not change its mass and speed but changes its direction of motion. So both velocity and momentum get changed.
The fact that magnetic field is produced around a wire carrying a current, was discovered by- a)Faraday
- b)Oersted
- c)Maxwell
- d)Joule.
Correct answer is option 'B'. Can you explain this answer?
The fact that magnetic field is produced around a wire carrying a current, was discovered by
a)
Faraday
b)
Oersted
c)
Maxwell
d)
Joule.
|
|
Ravi Sharma answered |
The correct answer is B as e electric current through the copper wire has produced a magnetic . In 1820 he accidentally discovered that a compass needle got deflected ... Through this observation Oersted showed that electricity and . representing the magnetic field around a current-carrying straight wire.
If the circuit is closed and magnetic field lines are drawn over the horizontal plane ABCD, the lines are
- a)concentric circles
- b)elliptical in shape
- c)straight lines parallel to each other
- d)concentric circles near the point O but of elliptical shapes as we go away from it
Correct answer is option 'A'. Can you explain this answer?
If the circuit is closed and magnetic field lines are drawn over the horizontal plane ABCD, the lines are
a)
concentric circles
b)
elliptical in shape
c)
straight lines parallel to each other
d)
concentric circles near the point O but of elliptical shapes as we go away from it
|
|
Anita Menon answered |
- When a circuit carrying current is closed, it generates a magnetic field around it.
- According to Ampère's circuital law and the right-hand rule, the magnetic field lines around a straight current-carrying conductor form concentric circles.
- These circles are centered on the wire, and their planes are perpendicular to the direction of the current.
- Therefore, on a horizontal plane like ABCD, the magnetic field lines appear as concentric circles, making option A correct.
- According to Ampère's circuital law and the right-hand rule, the magnetic field lines around a straight current-carrying conductor form concentric circles.
- These circles are centered on the wire, and their planes are perpendicular to the direction of the current.
- Therefore, on a horizontal plane like ABCD, the magnetic field lines appear as concentric circles, making option A correct.
The use of fuses in electric power-lines is :- a)to keep main voltage constant
- b)to open the line permanently when there is an overload
- c)(3) just to show an indication when there is an overload
- d)as a switch to use in an emergency
Correct answer is option 'B'. Can you explain this answer?
The use of fuses in electric power-lines is :
a)
to keep main voltage constant
b)
to open the line permanently when there is an overload
c)
(3) just to show an indication when there is an overload
d)
as a switch to use in an emergency
|
Ishan Khanna answered |
A fuse is used to break the circuit,in order to protect the electrical appliances from damage. In case of overcurrent a fuse melts and breaks the circuit and stops the current flowing through the components. A fuse is made up of a thin material which has a low melting point.
The strength of the magnetic field around a current-carrying straight conductor- a)is same every where around the conductor
- b)is directly proportional to the square of distance of a point from the conductor
- c)is directly proportional to the current flowing in the conductor
- d)is inversely proportional to the current
Correct answer is option 'C'. Can you explain this answer?
The strength of the magnetic field around a current-carrying straight conductor
a)
is same every where around the conductor
b)
is directly proportional to the square of distance of a point from the conductor
c)
is directly proportional to the current flowing in the conductor
d)
is inversely proportional to the current
|
|
Krishna Iyer answered |
The strength of the magnetic field around a current-carrying straight conductor is directly proportional to the amount of current flowing in the conductor.
When the direction of current through the conductor is reversed, the direction of- a)force is also reversed
- b)force remains same
- c)electromagnetic field is reversed
- d)electric field is also reversed
Correct answer is option 'A'. Can you explain this answer?
When the direction of current through the conductor is reversed, the direction of
a)
force is also reversed
b)
force remains same
c)
electromagnetic field is reversed
d)
electric field is also reversed
|
Drnitin Gopale answered |
Stretch out your hand as per Fleming left-hand rule and then tilt your hand upside down. You can see that the direction of mag field is the same, but the direction of current has reversed as per the question. also, the thumb goes downwards i.e opposite to initial direction. hence, we can see that the direction of force has been reversed.
The magnetic field lines inside a current carrying solenoid are :- a)along the axis and parallel to each other
- b)perpendicular to the axis and equidistant from each other
- c)circular and they do not intersect each other
- d)circular at the ends but they are parallel to the axis inside the solenoid
Correct answer is option 'A'. Can you explain this answer?
The magnetic field lines inside a current carrying solenoid are :
a)
along the axis and parallel to each other
b)
perpendicular to the axis and equidistant from each other
c)
circular and they do not intersect each other
d)
circular at the ends but they are parallel to the axis inside the solenoid
|
|
Krishna Iyer answered |
The magnetic field produced by a current carrying solenoid is similar to the magnetic field produced by a bar magnet. The magnetic field lines inside the solenoid are in the form of parallel straight lines and along the axis of solenoid.
When a fuse is rated at 8 A, it means :- a)it will not work if current is less than 8 A
- b)it has a resistance of 8 ohm
- c)it will work only if current is 8 A
- d)it will burn if current exceeds 8 A.
Correct answer is option 'D'. Can you explain this answer?
When a fuse is rated at 8 A, it means :
a)
it will not work if current is less than 8 A
b)
it has a resistance of 8 ohm
c)
it will work only if current is 8 A
d)
it will burn if current exceeds 8 A.
|
Rohit Chauhan answered |
It means that it will not work if current is less than 8A. It has a resistance of 8 ohm.
Same amount of current flows in the same direction .long the two parallel conductors separated by a small distance:- a)Both conductors attract each other
- b)Both conductors repel each other
- c)Conductors neither attract each other nor repel each other
- d)Both conductors rotates about their axis.
Correct answer is option 'A'. Can you explain this answer?
Same amount of current flows in the same direction .long the two parallel conductors separated by a small distance:
a)
Both conductors attract each other
b)
Both conductors repel each other
c)
Conductors neither attract each other nor repel each other
d)
Both conductors rotates about their axis.
|
Anshu Shah answered |
F/l is the force per unit length between two parallel currents I1 and I2 separated by a distance r. The force is attractive if the currents are in the same direction and repulsive if they are in opposite directions. This force is responsible for the pinch effect in electric arcs and plasmas.
Who has stated the Right hand Thumb Rule?- a)Orsted
- b)Fleming
- c)Einstein
- d)Maxwell
Correct answer is option 'D'. Can you explain this answer?
Who has stated the Right hand Thumb Rule?
a)
Orsted
b)
Fleming
c)
Einstein
d)
Maxwell
|
Asha Yadav answered |
B) Fleming
The right-hand thumb rule is a mnemonic technique used in electromagnetism to determine the direction of a magnetic field generated by a current-carrying conductor. It was first stated by John Ambrose Fleming, a British physicist and electrical engineer, in the late 19th century. The rule states that if the right hand is used to grip the conductor with the thumb pointing in the direction of the current flow, then the curled fingers will give the direction of the magnetic field.
The right-hand thumb rule is a mnemonic technique used in electromagnetism to determine the direction of a magnetic field generated by a current-carrying conductor. It was first stated by John Ambrose Fleming, a British physicist and electrical engineer, in the late 19th century. The rule states that if the right hand is used to grip the conductor with the thumb pointing in the direction of the current flow, then the curled fingers will give the direction of the magnetic field.
A constant current I flows through a horizontal metal wire in the plane of the paper from east to west as shown in the figure. The direction of magnetic field will be from north to south at a point :
- a)directly above the wire
- b)directly below the wire
- c)on the north side of the wire in the plane of the paper
- d)on the south side of the wire in the plane of the paper
Correct answer is option 'B'. Can you explain this answer?
A constant current I flows through a horizontal metal wire in the plane of the paper from east to west as shown in the figure. The direction of magnetic field will be from north to south at a point :
a)
directly above the wire
b)
directly below the wire
c)
on the north side of the wire in the plane of the paper
d)
on the south side of the wire in the plane of the paper
|
|
Ananya Das answered |
Let a constant current I flows through a horizontal wire from east to west. The direction of magnetic field, as per right-hand thumb rule, will be from north to south at a point directly below the current-carrying wire.
When current is circular, the associated magnetic field is- a)Straight
- b)Elliptical
- c)Circular
- d)Parabolic.
Correct answer is option 'A'. Can you explain this answer?
When current is circular, the associated magnetic field is
a)
Straight
b)
Elliptical
c)
Circular
d)
Parabolic.
|
Ananya Kumar answered |
When current flows through a straight conductor, it is said that the current is straight. The magnetic field produced due to a straight current carrying conductor is in the form of concentric circles. The centre of the circles lies on the conductor itself and are in the plane perpendicular to the straight conductor. This implies that the magnetic field produced due to straight current is circular.
In all the electrical appliances, the switches are put in the- a)neutral wire
- b)earth wire
- c)live wire
- d)all of above
Correct answer is option 'C'. Can you explain this answer?
In all the electrical appliances, the switches are put in the
a)
neutral wire
b)
earth wire
c)
live wire
d)
all of above
|
|
Vikram Kapoor answered |
If the switch is placed in the neutral wire, the electrical appliance is still connected to the high voltage live wire even when the switch is opened.)
This may cause the user to get an electric shock if he touches the live wire.
That’s why the switches are put in the live wire.
This may cause the user to get an electric shock if he touches the live wire.
That’s why the switches are put in the live wire.
In domestic electric circuits, fuse must be placed in series with- a)Earth wire
- b)Neutral wire
- c)Live wire
- d)Any of the three wires
Correct answer is option 'C'. Can you explain this answer?
In domestic electric circuits, fuse must be placed in series with
a)
Earth wire
b)
Neutral wire
c)
Live wire
d)
Any of the three wires
|
Pooja Choudhury answered |
The fuse wire is always connected in the live wire of the circuit because if the fuse is put in the neutral wire, then due to excessive flow of current when the fuse burns, current stops flowing in the circuit, but the appliance remains connected to the high potential point of supply through the live wire .
The area around a magnet, in which its influence (force of attraction or repulsion) can be felt, is called its- a)magnetic field
- b)magnetic strength
- c)magnetic power
- d)magnetic intensity
Correct answer is option 'A'. Can you explain this answer?
The area around a magnet, in which its influence (force of attraction or repulsion) can be felt, is called its
a)
magnetic field
b)
magnetic strength
c)
magnetic power
d)
magnetic intensity
|
|
Akshara kulkarni answered |
The region around a magnet, in which its influence can be felt, is called its magnetic field
Choose the wrong statement out of the following :- a)Magnetic poles always exist in pairs
- b)Magnetic poles must have same magnetic strength
- c)Like magnetic poles attract each other
- d)Unlike magnetic poles attract each other
Correct answer is option 'C'. Can you explain this answer?
Choose the wrong statement out of the following :
a)
Magnetic poles always exist in pairs
b)
Magnetic poles must have same magnetic strength
c)
Like magnetic poles attract each other
d)
Unlike magnetic poles attract each other
|
|
Anoushka nair answered |
Like magnetic poles (say N- and N-poles) always repel each other.
For a solenoid carrying a current I and having n turns per unit length, wrapped on a core of permeability ?,the correct expression for magnetic field intensity (2) is- a)B=μo/μ nI
- b)B=μoμI/n
- c) B = μoμnI
- d) B = μoμn / I
Correct answer is option 'C'. Can you explain this answer?
For a solenoid carrying a current I and having n turns per unit length, wrapped on a core of permeability ?,
the correct expression for magnetic field intensity (2) is
a)
B=μo/μ nI
b)
B=μoμI/n
c)
B = μoμnI
d)
B = μoμn / I
|
Janhavi Chakraborty answered |
A simple electromagnet can be created by wrapping a coil of wire around a soft iron The magnetic field strength of an electromagnet is therefore determined by the turns of wire in the coil the greater will be the strength of the magnetic field.
The direction of magnetic field developed around a current-carrying conductor can be easily found by the use of- a)Right-hand thumb rule
- b)Left-hand thumb rule
- c)Fleming’s left-hand rule
- d)Fleming’s right-hand rule
Correct answer is option 'A'. Can you explain this answer?
The direction of magnetic field developed around a current-carrying conductor can be easily found by the use of
a)
Right-hand thumb rule
b)
Left-hand thumb rule
c)
Fleming’s left-hand rule
d)
Fleming’s right-hand rule
|
|
Arun Sharma answered |
The direction of magnetic field developed around a current-carrying conductor can be found by the use of right-hand thumb rule.
For a current in a long straight solenoid N-pole and S-poIe are created at the two ends. Among the following statements, the incorrect statement is- a)The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid.
- b)The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil.
- c)The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.
- d)The N-pole and S-pole exchange position when the direction of current through the solenoid is reversed.
Correct answer is option 'C'. Can you explain this answer?
For a current in a long straight solenoid N-pole and S-poIe are created at the two ends. Among the following statements, the incorrect statement is
a)
The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid.
b)
The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil.
c)
The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.
d)
The N-pole and S-pole exchange position when the direction of current through the solenoid is reversed.
|
|
Ananya Das answered |
A solenoid behaves like a bar magnet. Hence the pattern of magnetic field associated with solenoid and around the bar magnet is same.
When the main switch of the house circuit is put off, it disconnects the :- a)live wire
- b)neutral wire
- c)earth wire
- d)live and neutral wires.
Correct answer is option 'D'. Can you explain this answer?
When the main switch of the house circuit is put off, it disconnects the :
a)
live wire
b)
neutral wire
c)
earth wire
d)
live and neutral wires.
|
|
Priya Sengupta answered |
The correct option is D.
In this case when the main switch of the house is switched off it would disconnect the live wire and the neutral wire.
In this case when the main switch of the house is switched off it would disconnect the live wire and the neutral wire.
When current flows anticlockwise in a loop the magnetic polarity of the face is- a)East
- b)South
- c)West
- d)North.
Correct answer is option 'D'. Can you explain this answer?
When current flows anticlockwise in a loop the magnetic polarity of the face is
a)
East
b)
South
c)
West
d)
North.
|
|
Naina Sharma answered |
The polarity of this magnet can be understood with the help of clock face rule. If the current is flowing in anti-clockwise direction, then the face of the loop shows North pole.
The strength of magnetic field along the axis of a solenoid coil :- a)increases on increasing current flowing through the solenoid coil
- b)increases on increasing the number of turns in the solenoid coil
- c)increases on introducing a soft iron core inside the solenoid coil
- d)all of the above
Correct answer is option 'D'. Can you explain this answer?
The strength of magnetic field along the axis of a solenoid coil :
a)
increases on increasing current flowing through the solenoid coil
b)
increases on increasing the number of turns in the solenoid coil
c)
increases on introducing a soft iron core inside the solenoid coil
d)
all of the above
|
Pallavi kulkarni answered |
The strength of magnetic field along the axis of a solenoid coil increases on increasing the current flowing through the solenoid coil and on increasing the number of turns in the solenoid coil. Moreover, if a soft iron core is inserted inside the solenoid coil then magnetic field increases many fold.
Due to overloading, the current in circuit becomes- a)Less
- b)More
- c)Zero
- d)Not definite
Correct answer is option 'B'. Can you explain this answer?
Due to overloading, the current in circuit becomes
a)
Less
b)
More
c)
Zero
d)
Not definite
|
|
Swara Nambiar answered |
Explanation:
When a circuit is overloaded, it means that the current flowing through it exceeds its rated capacity. This can happen when too many devices are connected to a circuit that cannot handle the load.
Effects of Overloading:
1. Increased Current: When a circuit is overloaded, the current flowing through it increases. This is because the devices connected to the circuit draw more current than the circuit is designed to handle.
2. Heat Generation: The increased current leads to increased heat generation in the circuit components, such as wires, switches, and connectors. This can cause damage to the components and increase the risk of fire.
3. Voltage Drop: Overloading can also lead to a voltage drop in the circuit. This means that the voltage supplied to the devices connected to the circuit decreases, which can affect their performance.
Effect on Current:
The correct answer to the given question is option 'B' - More. When a circuit is overloaded, the current flowing through it increases. This is because the devices connected to the circuit draw more current than the circuit can provide.
Reason:
The reason behind the increase in current is Ohm's Law, which states that the current flowing through a circuit is directly proportional to the voltage and inversely proportional to the resistance. When the voltage supplied to the circuit remains constant and the resistance of the circuit remains the same, an increase in current can only occur if the devices connected to the circuit draw more current.
Therefore, when a circuit is overloaded, the current flowing through it becomes more than the rated capacity of the circuit. This can lead to overheating, voltage drop, and damage to the circuit components. It is important to avoid overloading circuits to ensure their safe and efficient operation.
When a circuit is overloaded, it means that the current flowing through it exceeds its rated capacity. This can happen when too many devices are connected to a circuit that cannot handle the load.
Effects of Overloading:
1. Increased Current: When a circuit is overloaded, the current flowing through it increases. This is because the devices connected to the circuit draw more current than the circuit is designed to handle.
2. Heat Generation: The increased current leads to increased heat generation in the circuit components, such as wires, switches, and connectors. This can cause damage to the components and increase the risk of fire.
3. Voltage Drop: Overloading can also lead to a voltage drop in the circuit. This means that the voltage supplied to the devices connected to the circuit decreases, which can affect their performance.
Effect on Current:
The correct answer to the given question is option 'B' - More. When a circuit is overloaded, the current flowing through it increases. This is because the devices connected to the circuit draw more current than the circuit can provide.
Reason:
The reason behind the increase in current is Ohm's Law, which states that the current flowing through a circuit is directly proportional to the voltage and inversely proportional to the resistance. When the voltage supplied to the circuit remains constant and the resistance of the circuit remains the same, an increase in current can only occur if the devices connected to the circuit draw more current.
Therefore, when a circuit is overloaded, the current flowing through it becomes more than the rated capacity of the circuit. This can lead to overheating, voltage drop, and damage to the circuit components. It is important to avoid overloading circuits to ensure their safe and efficient operation.
Magnetic field produced at the centre of a current carrying circular wire is :- a)Directly proportional to the square of the radius of the circular wire
- b)Directly proportional to the radius of the circular wire
- c)Inversely proportional to the square of the radius of the circular wire
- d)none of these
Correct answer is option `D`. Can you explain this answer?
Magnetic field produced at the centre of a current carrying circular wire is :
a)
Directly proportional to the square of the radius of the circular wire
b)
Directly proportional to the radius of the circular wire
c)
Inversely proportional to the square of the radius of the circular wire
d)
none of these
|
|
Shubham Joshi answered |
ANSWER :
- a)Directly proportional to the square of the radius of the circular wire
Direction of induced current produced by motion of a conductor in a magnetic field is given by- a)Fleming's right hand rule
- b)Fleming's left hand rule
- c)Lenz's rule
- d)Faraday's rule.
Correct answer is option 'A'. Can you explain this answer?
Direction of induced current produced by motion of a conductor in a magnetic field is given by
a)
Fleming's right hand rule
b)
Fleming's left hand rule
c)
Lenz's rule
d)
Faraday's rule.
|
|
Vikas Kumar answered |
In an electric generator mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. Fleming's right hand rule is used where motion and magnetic field is given and the current is induced.
The strength of a magnetic field inside a long current-carrying straight solenoid coil is- a)more at the ends than at the centre
- b)minimum in the middle
- c)same at all points
- d)found to increase from one end to the other
Correct answer is option 'C'. Can you explain this answer?
The strength of a magnetic field inside a long current-carrying straight solenoid coil is
a)
more at the ends than at the centre
b)
minimum in the middle
c)
same at all points
d)
found to increase from one end to the other
|
|
Rajani dasgupta answered |
The strength of a magnetic field inside a long, current-carrying, straight solenoid is uniform at all points. Moreover, the field depends on the amount of current flowing and the number of turns in solenoid coil besides its length
The most important safety method used for protecting home appliances from short circuiting or overloading is- a)earthing
- b)use of fuse
- c)use of stabilizers
- d)use of electric meter
Correct answer is option 'B'. Can you explain this answer?
The most important safety method used for protecting home appliances from short circuiting or overloading is
a)
earthing
b)
use of fuse
c)
use of stabilizers
d)
use of electric meter
|
Niharika Mehta answered |
The most important safety, method used for protecting home appliances from short circuiting or overloading is the electric fuse. This is a safety device having thin wire of short length made of tin (25%) and lead (75%) alloy having low melting point around 200degree. The fuse wire is of chosen thickness, so as to fix its resistance and hence amount of heating on passage of a particular amount of current. Whenever current through the fuse exceeds the set limit, the fuse wire melts and breaks the circuit. This saves the main circuit components from damage.
A current-carrying conductor is placed perpendicular to the direction of a uniform magnetic field. The direction of force acting on the conductor due to magnetic field is given by- a)Maxwell’s cork screw rule
- b)Ampere’s rule
- c)Fleming’s left-hand rule
- d)Fleming’s right-hand rule
Correct answer is option 'C'. Can you explain this answer?
A current-carrying conductor is placed perpendicular to the direction of a uniform magnetic field. The direction of force acting on the conductor due to magnetic field is given by
a)
Maxwell’s cork screw rule
b)
Ampere’s rule
c)
Fleming’s left-hand rule
d)
Fleming’s right-hand rule
|
Parth Basu answered |
A current carrying conductor when placed at right angle to a magnetic field, experiences a force due to a which we get motion. The direction of the force is given by Fleming’s left hand rule.
Assertion (A): The direction of force on a current-carrying conductor placed in a magnetic field depends on the direction of both the current and the magnetic field.Reason (R): When the direction of the current through the conductor is perpendicular to the direction of the magnetic field, the force experienced by the conductor is at its maximum.- a)If both Assertion and Reason are true and Reason is the correct explanation of Assertion
- b)If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
- c)If Assertion is true but Reason is false
- d)If both Assertion and Reason are false
Correct answer is option 'B'. Can you explain this answer?
Assertion (A): The direction of force on a current-carrying conductor placed in a magnetic field depends on the direction of both the current and the magnetic field.
Reason (R): When the direction of the current through the conductor is perpendicular to the direction of the magnetic field, the force experienced by the conductor is at its maximum.
a)
If both Assertion and Reason are true and Reason is the correct explanation of Assertion
b)
If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
c)
If Assertion is true but Reason is false
d)
If both Assertion and Reason are false
|
Kamna Science Academy answered |
- The assertion that the force on a current-carrying conductor in a magnetic field depends on the directions of both the current and the magnetic field is correct. This relationship is described by the right-hand rule for the force on a current-carrying conductor in a magnetic field.
- The reason that the force is maximum when the current is perpendicular to the magnetic field is also correct. This is a fundamental principle of electromagnetism.
- However, the reason does not directly explain why the assertion is true. While it is true that the force is maximum when the current is perpendicular to the magnetic field, this fact alone does not fully explain the dependence of the force on the directions of both the current and the magnetic field. Hence, Option B is the correct answer.
Assertion (A): The magnetic field lines around a bar magnet are closed curves.Reason (R): Inside the magnet, the direction of field lines is from its south pole to its north pole.- a)If both Assertion and Reason are true and Reason is the correct explanation of Assertion
- b)If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
- c)If Assertion is true but Reason is false
- d)If both Assertion and Reason are false
Correct answer is option 'B'. Can you explain this answer?
Assertion (A): The magnetic field lines around a bar magnet are closed curves.
Reason (R): Inside the magnet, the direction of field lines is from its south pole to its north pole.
a)
If both Assertion and Reason are true and Reason is the correct explanation of Assertion
b)
If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
c)
If Assertion is true but Reason is false
d)
If both Assertion and Reason are false
|
Elite Coaching Classes answered |
- Assertion (A) is true; magnetic field lines around a bar magnet are indeed closed curves.
- Reason (R) is also true; inside the magnet, the direction of field lines runs from its south pole to its north pole.
- However, the Reason does not correctly explain Assertion, as the closure of field lines is a consequence of the overall magnetic field configuration rather than just the direction of the field lines inside the magnet.
In a three pin socket (shoe) the bigger hole is connected to- a)Any wire
- b)Live wire
- c)Neutral wire
- d)Earth wire
Correct answer is option 'D'. Can you explain this answer?
In a three pin socket (shoe) the bigger hole is connected to
a)
Any wire
b)
Live wire
c)
Neutral wire
d)
Earth wire
|
|
Niharika Mishra answered |
The bigger hole is connected to the earth wire and the other two holes are connected to the live wire and neutral wire respectively.
Current flowing in conductor A is 2A and current flowing in conductor B is 4A. The ratio of magnetic field produced aroundconductor A to the magnetic field produced around conductor B at a distance 10 cm from both the conductors is:- a)2 : 1
- b)1 : 2
- c)4 : 1
- d) √2 :1
Correct answer is option 'B'. Can you explain this answer?
Current flowing in conductor A is 2A and current flowing in conductor B is 4A. The ratio of magnetic field produced around
conductor A to the magnetic field produced around conductor B at a distance 10 cm from both the conductors is:
a)
2 : 1
b)
1 : 2
c)
4 : 1
d)
√2 :1
|
Sima Mandal answered |
Because both of them have current flowing through them in equal ratio. i1: i2 = mag1: mag2
When the current is passing through the straight wire then, the associated magnetic field is- a)Straight
- b)Elliptica
- c)Circular
- d)Parabolic.
Correct answer is option 'C'. Can you explain this answer?
When the current is passing through the straight wire then, the associated magnetic field is
a)
Straight
b)
Elliptica
c)
Circular
d)
Parabolic.
|
|
Rajiv Gupta answered |
The magnetic field around a straight current carrying conductor or wire can be increased by bending the wire into circular loop.
A circular loop is made up of large number of very small straight wires.A magnetic field is produced by an electric current flowing through a circular coil of wire.Each small section of current carrying wire contributes to magnetic field lines.
At the centre of circular wire,field lines become straight and perpendicular to the plane of coil.Right hand thumb rule is used to determine the direction of magnetic field produced due to current carrying circular wire.
Assertion (A): When a circular loop of wire lies in the plane of the table with current passing through it clockwise, the magnetic field direction inside and outside the loop can be determined using the right-hand rule.Reason (R): The magnetic field in a given region is uniform.- a)If both Assertion and Reason are true and Reason is the correct explanation of Assertion
- b)If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
- c)If Assertion is true but Reason is false
- d)If both Assertion and Reason are false
Correct answer is option 'B'. Can you explain this answer?
Assertion (A): When a circular loop of wire lies in the plane of the table with current passing through it clockwise, the magnetic field direction inside and outside the loop can be determined using the right-hand rule.
Reason (R): The magnetic field in a given region is uniform.
a)
If both Assertion and Reason are true and Reason is the correct explanation of Assertion
b)
If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
c)
If Assertion is true but Reason is false
d)
If both Assertion and Reason are false
|
|
Kavya Shah answered |
Assertion Analysis
The assertion states that when a circular loop of wire carries a clockwise current, the magnetic field direction inside and outside the loop can be determined using the right-hand rule. This is correct:
- When you curl the fingers of your right hand in the direction of the current (clockwise in this case), your thumb points downward, indicating that the magnetic field inside the loop is directed downwards.
- Outside the loop, the magnetic field lines point outwards, following the right-hand rule.
Thus, the assertion is true.
Reason Analysis
The reason provided claims that the magnetic field in a given region is uniform. This statement is not necessarily true:
- The magnetic field produced by a circular loop is not uniform; it varies in strength and direction depending on the position in relation to the loop.
- Inside the loop, the magnetic field is relatively uniform compared to the outside, but it is not uniform across the entire region.
Therefore, while the assertion is true, the reason is false.
Conclusion
Combining these analyses leads to the conclusion:
- Both the assertion and reason are not correctly aligned in terms of explanation.
- Thus, the correct answer is option 'B': both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
This separation of understanding clarifies the relationship between the magnetic field's behavior around a current-carrying loop and the misconceptions about uniformity in magnetic fields.
The assertion states that when a circular loop of wire carries a clockwise current, the magnetic field direction inside and outside the loop can be determined using the right-hand rule. This is correct:
- When you curl the fingers of your right hand in the direction of the current (clockwise in this case), your thumb points downward, indicating that the magnetic field inside the loop is directed downwards.
- Outside the loop, the magnetic field lines point outwards, following the right-hand rule.
Thus, the assertion is true.
Reason Analysis
The reason provided claims that the magnetic field in a given region is uniform. This statement is not necessarily true:
- The magnetic field produced by a circular loop is not uniform; it varies in strength and direction depending on the position in relation to the loop.
- Inside the loop, the magnetic field is relatively uniform compared to the outside, but it is not uniform across the entire region.
Therefore, while the assertion is true, the reason is false.
Conclusion
Combining these analyses leads to the conclusion:
- Both the assertion and reason are not correctly aligned in terms of explanation.
- Thus, the correct answer is option 'B': both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
This separation of understanding clarifies the relationship between the magnetic field's behavior around a current-carrying loop and the misconceptions about uniformity in magnetic fields.
What defines a solenoid in the context of magnetic fields?- a)A coil of a few circular turns
- b)A long, straight wire
- c)A coil of many circular turns of insulated wire
- d)A single loop of wire
Correct answer is option 'C'. Can you explain this answer?
What defines a solenoid in the context of magnetic fields?
a)
A coil of a few circular turns
b)
A long, straight wire
c)
A coil of many circular turns of insulated wire
d)
A single loop of wire
|
|
Elite Coaching Classes answered |
In the context of magnetic fields, a solenoid is defined as a coil of many circular turns of insulated wire. Solenoids are crucial components in electromagnets and various electrical devices due to their ability to generate strong and uniform magnetic fields.
Chapter doubts & questions for Simple Circuits - Science for Grade 8 2025 is part of Grade 8 exam preparation. The chapters have been prepared according to the Grade 8 exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for Grade 8 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.
Chapter doubts & questions of Simple Circuits - Science for Grade 8 in English & Hindi are available as part of Grade 8 exam.
Download more important topics, notes, lectures and mock test series for Grade 8 Exam by signing up for free.
Science for Grade 8
76 videos|170 docs|65 tests
|
|
© EduRev
|
Education Revolution
|
|
Signup to see your scores
go up
within 7 days!
within 7 days!
Takes less than 10 seconds to signup