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All questions of Electricity for Class 10 Exam
To get 2Ω resistance using only 6Ω resistors, the number of them required is- a)2
- b)3
- c)4
- d)6
Correct answer is option 'B'. Can you explain this answer?
To get 2Ω resistance using only 6Ω resistors, the number of them required is
a)
2
b)
3
c)
4
d)
6
 | Avinash Patel answered |
Three resistors of 2Ω is required to get 6Ω because resultant is more than individual so they all must be connected in series.
The effective resistance between A and B is
- a)4Ω
- b)6Ω
- c)May be 10Ω
- d)Must be 10Ω
Correct answer is option 'A'. Can you explain this answer?
The effective resistance between A and B is
a)
4Ω
b)
6Ω
c)
May be 10Ω
d)
Must be 10Ω
 | Gaurav Kumar answered |
6Ω is shorted
as current will pass from wire having no resistance
so effective resistance is 4Ω.
as current will pass from wire having no resistance
so effective resistance is 4Ω.
The potential difference of a circuit is constant. If the resistance of a circuit is doubled, then its current will become;- a)4 I
- b)I/2
- c)2 I
- d)I
Correct answer is 'B'. Can you explain this answer?
The potential difference of a circuit is constant. If the resistance of a circuit is doubled, then its current will become;
a)
4 I
b)
I/2
c)
2 I
d)
I
 | Nisha Choudhury answered |
According to ohm's law
Current (I) = Potential difference (V) / Resistance(R)
If the potential difference is maintained constant and the resistance is changed,
Cureent (I) is inversely proportinal to the reisistance (R)
V = IR --(1)
Now, here V is constant.
Let , new resistance R' = 2R and assume that current flow be I'
So, from (1),
IR = I'. R',
=> IR = I'. 2R,
Therefore, I' = I / 2
So,
If the resistance is doubled by applying the constant potential difference the current becomes the half of the previous.
An electric refrigerator rated 500 W operates 10 hr per day. What is the cost of the energy to operate it for 30 days at Rs. 4.00 per kWh?- a)Rs. 600
- b)Rs. 400
- c)Rs. 500
- d)Rs. 800
Correct answer is option 'A'. Can you explain this answer?
An electric refrigerator rated 500 W operates 10 hr per day. What is the cost of the energy to operate it for 30 days at Rs. 4.00 per kWh?
a)
Rs. 600
b)
Rs. 400
c)
Rs. 500
d)
Rs. 800
| | Aditya Shah answered |
E = P × t = 0.5 × 10 × 30 = 150 kWh
Cost of energy = 150 × 4 = Rs. 600
Cost of energy = 150 × 4 = Rs. 600
Calculate the current flows through the 10Ω resistor in the following circuit.
- a)1.2A
- b)0.6A
- c)0.2A
- d)2.0A
Correct answer is option 'B'. Can you explain this answer?
Calculate the current flows through the 10Ω resistor in the following circuit.
a)
1.2A
b)
0.6A
c)
0.2A
d)
2.0A
 | Sun Ray Institute answered |
In parallel, potential difference across each resistor will remain same. So, current through 10Ω resistor
If four resistors each of 1Ω are connected in parallel, the effective resistance will be- a)0.5Ω
- b)0.25Ω
- c)4Ω
- d)2Ω
Correct answer is option 'B'. Can you explain this answer?
If four resistors each of 1Ω are connected in parallel, the effective resistance will be
a)
0.5Ω
b)
0.25Ω
c)
4Ω
d)
2Ω
| | Gaurav Kumar answered |
If four resistors each of 1Ω are connected in parallel, the effective resistance will be 0.25Ω..
As, in parralel connection,
1/Reff. = 1/R1 + 1/R2 + ....
Conventional direction of electric current is from- a)Lower potential to higher potential
- b)Higher resistance to lower resistance
- c)Positive to negative terminal
- d)Negative to positive terminal
Correct answer is 'C'. Can you explain this answer?
Conventional direction of electric current is from
a)
Lower potential to higher potential
b)
Higher resistance to lower resistance
c)
Positive to negative terminal
d)
Negative to positive terminal
 | C K Academy answered |
The current in the wire is due to the drifting of electrons inside a wire in a direction opposite to the flow of electrons. During their drifting they collide with their atoms vibrating about their mean position and lose some of kinetic energy to the vibrating atoms.
The electrons are negatively charged particles and so, the electrons move towards the positively charged terminal from the negatively charged terminal.
Hence, the statement is true as the conventional direction of flow of current is from positive terminal to negative terminal of the cell.
The electrons are negatively charged particles and so, the electrons move towards the positively charged terminal from the negatively charged terminal.
Hence, the statement is true as the conventional direction of flow of current is from positive terminal to negative terminal of the cell.
The water heating rod draws 10 A current when connected to certain power source. The resistance of rod is 12 Ω. The source voltage is:- a)1.2 V
- b)120 V
- c)1200 V
- d)None of these
Correct answer is option 'B'. Can you explain this answer?
The water heating rod draws 10 A current when connected to certain power source. The resistance of rod is 12 Ω. The source voltage is:
a)
1.2 V
b)
120 V
c)
1200 V
d)
None of these
| | Aditya Kumar answered |
The correct answer is B as Ohm's law:
voltage=current x resistance=12x10=120 V
voltage=current x resistance=12x10=120 V
Can you explain the answer of this question below:How much work is done, when 1 coulomb of charge moves against a potential difference of 1 volt?
- A:
1 joule
- B:
2 joule
- C:
0.5 joule
- D:
1.5 joule
The answer is a.
How much work is done, when 1 coulomb of charge moves against a potential difference of 1 volt?
1 joule
2 joule
0.5 joule
1.5 joule
| | Arun Yadav answered |
Charge moved, Q = 1 C
Potential difference, V = 1V
Therefore,
Work done, W = QV
= 1 C x 1 V
= 1 joule.
A wire of resistance 8Ω is bent in the form of a closed circle. What is the effective resistance between the two points A and B, at the ends of any diameter of the circle ?
- a)8Ω
- b)4Ω
- c)2Ω
- d)1Ω
Correct answer is option 'C'. Can you explain this answer?
A wire of resistance 8Ω is bent in the form of a closed circle. What is the effective resistance between the two points A and B, at the ends of any diameter of the circle ?
a)
8Ω
b)
4Ω
c)
2Ω
d)
1Ω
 | Flembe Academy answered |
When a wire of 8Ω resistance is bent in the form of a closed circle, resistance of each half (semicircular) part is 8/2 Ω = 4Ω.
As these two parts are connected in parallel across points A and B, hence effective resistance will be 2Ω.
As these two parts are connected in parallel across points A and B, hence effective resistance will be 2Ω.
The resistance whose V - I graph is given below is
- a)
- b)
- c)
- d)
Correct answer is option 'B'. Can you explain this answer?
The resistance whose V - I graph is given below is
a)
b)
c)
d)
 | Prachi shukla answered |
Resistance = slope line of V-I graph
A resistance wire is stretched so as to double its length. Its new resistivity will have a magnitude- a)2 times its original value
- b)4 times its original value
- c)8 times its original valu
- d)same as its original value
Correct answer is option 'D'. Can you explain this answer?
A resistance wire is stretched so as to double its length. Its new resistivity will have a magnitude
a)
2 times its original value
b)
4 times its original value
c)
8 times its original valu
d)
same as its original value
| | Anita Menon answered |
When a wire is stretched, its resistivity remains unchanged. It is because resistivity of a conductor depends only on its material and is independent of its length or cross- section area.
A cooler of 1500 W, 200 volt and a fan of 500 W, 200 volt are to be used from a household supply. The rating of fuse to be used is- a)2.5 A
- b)5.0 A
- c)7.5 A
- d)10 A
Correct answer is option 'D'. Can you explain this answer?
A cooler of 1500 W, 200 volt and a fan of 500 W, 200 volt are to be used from a household supply. The rating of fuse to be used is
a)
2.5 A
b)
5.0 A
c)
7.5 A
d)
10 A
 | Shreyas murthy answered |
Total power used, P - P1 + P2 = 1500 + 500 = 2000 W.
Current drawn from the supply,
Current drawn from the supply,
All elements of an electric circuit are connected in series except :- a)voltmeter
- b)ammeter
- c)rheostat
- d)resistor
Correct answer is option 'A'. Can you explain this answer?
All elements of an electric circuit are connected in series except :
a)
voltmeter
b)
ammeter
c)
rheostat
d)
resistor
 | Ishan Choudhury answered |
In an electric circuit all other elements are connected in series but a voltmeter is connected in parallel.
Two devices are connected between two points say A and B in parallel. The physical quantity that will remain the same between the two points is- a)current
- b)voltage
- c)resistance
- d)None of these
Correct answer is option 'B'. Can you explain this answer?
Two devices are connected between two points say A and B in parallel. The physical quantity that will remain the same between the two points is
a)
current
b)
voltage
c)
resistance
d)
None of these
 | Meera Rana answered |
In parallel combination voltage remains same across two points.
A bulb draws a current of 0.20 A for 15 minutes. What is the amount of electric charge that flows through it ?- a)180 C
- b)182 C
- c)200 C
- d)300 C
Correct answer is option 'A'. Can you explain this answer?
A bulb draws a current of 0.20 A for 15 minutes. What is the amount of electric charge that flows through it ?
a)
180 C
b)
182 C
c)
200 C
d)
300 C
| | Rajiv Gupta answered |
The amount of electric charge that flows through the bulb =180 C.
How much heat energy is produced in 10 second in an electric iron having resistance 440 Ω, when a potential difference of 220 volt is applied across it?- a)1200 J
- b)600 J
- c)1000 J
- d)1100 J
Correct answer is option 'D'. Can you explain this answer?
How much heat energy is produced in 10 second in an electric iron having resistance 440 Ω, when a potential difference of 220 volt is applied across it?
a)
1200 J
b)
600 J
c)
1000 J
d)
1100 J
 | Imk Pathshala answered |
From ohm’s law, I = V/R = 220/440 = 0.5 A
H = I2 × R × t = (0.5)2 × 440 × 10 = 1100 J
A combination of three resistances has been shown here. Effective resistance between the points A and B is
- a)8Ω
- b)4Ω
- c)2Ω
- d)1Ω
Correct answer is option 'C'. Can you explain this answer?
A combination of three resistances has been shown here. Effective resistance between the points A and B is
a)
8Ω
b)
4Ω
c)
2Ω
d)
1Ω
 | Pooja Shah answered |
Value of series combination of 2Ω and 2Ω resistances = 4Ω. As it is now connected in parallel to 4Ω resistance, hence the effective resistance R between the points A and B will be
How much energy is transferred when 10 A current flows through a resistor of 5 ohm for 30 minutes?- a)0.25 kWh
- b)1.2 kWh
- c)0.025 kWh
- d)3.2 kWh
Correct answer is option 'A'. Can you explain this answer?
How much energy is transferred when 10 A current flows through a resistor of 5 ohm for 30 minutes?
a)
0.25 kWh
b)
1.2 kWh
c)
0.025 kWh
d)
3.2 kWh
| | Pooja Shah answered |
P = I2 R = (10)2 × 5 = 500 watt = 0.5 kW
t = 30 minute = 0.5 hr
E = P × t = 0.5 kW × 0.5 hr = 0.25 kWh
SI unit of resistivity is- a)ohm/metre
- b)ohm-metre
- c)ohm/(metre)3
- d)ohm/(metre)2
Correct answer is option 'B'. Can you explain this answer?
SI unit of resistivity is
a)
ohm/metre
b)
ohm-metre
c)
ohm/(metre)3
d)
ohm/(metre)2
 | Krishna Iyer answered |
As resistivity of the material of a resistor of length l, cross-section area A and resistance R is given by :ρ = R.A/I, hence SI unit of resistivity is ohm -metre (Ω m).
The opposing capacity of materials against the current flow is- a)Conductance
- b)Inductance
- c)Susceptance
- d)Resistance
Correct answer is option 'D'. Can you explain this answer?
The opposing capacity of materials against the current flow is
a)
Conductance
b)
Inductance
c)
Susceptance
d)
Resistance
 | Crafty Classes answered |
The electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor.
Resistance in a conductor can be defined as the opposition offered to the flow of electrons. For a conductor of uniform cross-sectional area resistance is directly proportional to the length of the conductor and inversely proportional to the cross-sectional area of the conductor.
The resistance of a conductor increases with-
I: Increase in length
II: Increase in volume
III: Decrease in area- a)I or III
- b)II only
- c)I or II
- d)III only
Correct answer is option 'A'. Can you explain this answer?
The resistance of a conductor increases with-
I: Increase in length
II: Increase in volume
III: Decrease in area
I: Increase in length
II: Increase in volume
III: Decrease in area
a)
I or III
b)
II only
c)
I or II
d)
III only
| | 💐 answered |
Resistance is directly proportional to Length nd inversely proportional to Area
Hence , resistance increase with increase in area nd increases with decrease in area !!!
Hence , resistance increase with increase in area nd increases with decrease in area !!!
A coil in the heater consume power P on passing current. If it is cut into halves and joined in parallel, it will consume power- a)P
- b)P/2
- c)2P
- d)4P
Correct answer is option 'D'. Can you explain this answer?
A coil in the heater consume power P on passing current. If it is cut into halves and joined in parallel, it will consume power
a)
P
b)
P/2
c)
2P
d)
4P
| | Pooja Shah answered |
Original power consumed, P = V2/R
When used in parallel
RP = R/4
∴ New power consumed when two halves in parallel
When used in parallel
RP = R/4
∴ New power consumed when two halves in parallel
A fuse wire repeatedly gets burnt when used with a good heater. It is advised to use a fuse wire of- a)more length
- b)less radius
- c)less length
- d)more radius
Correct answer is option 'D'. Can you explain this answer?
A fuse wire repeatedly gets burnt when used with a good heater. It is advised to use a fuse wire of
a)
more length
b)
less radius
c)
less length
d)
more radius
| | Pallavi kapoor answered |
In order to get the working of heater properly, fused wire of higher rating must be used.
A certain wire has a resistance R. The resistance of another wire identical with the first and having twice its diameter is;- a)0.5 R
- b)0.25 R
- c)4 R
- d)2 R
Correct answer is option 'B'. Can you explain this answer?
A certain wire has a resistance R. The resistance of another wire identical with the first and having twice its diameter is;
a)
0.5 R
b)
0.25 R
c)
4 R
d)
2 R
| | Rahul Kapoor answered |
Resistance of a wire is inversely proportional to the cross−sectional area:
R α 1/A
α 1/πd^2/4
α 1/d^2
R'/R = (d/d')^2
R'= R(d/2d)^2
= R/4
= 0.25 R
The resistance of an alloy :- a)increases with temperature
- b)decreases with temperature
- c)is constant with rise in temperature
- d)is zero
Correct answer is option 'A'. Can you explain this answer?
The resistance of an alloy :
a)
increases with temperature
b)
decreases with temperature
c)
is constant with rise in temperature
d)
is zero
| | Bibek Iyer answered |
The resistance of an alloy increases with temperature.
When an electric current flows through a material, it encounters resistance, which is the opposition to the flow of electric charge. The resistance of a material depends on various factors, including temperature.
The resistance of most materials, including metals and alloys, increases with an increase in temperature. This phenomenon is referred to as the positive temperature coefficient of resistance.
Factors contributing to the increase in resistance with temperature:
As the temperature of a material increases, the atoms or ions in the material gain thermal energy and start vibrating more vigorously. This increased atomic vibration leads to more frequent collisions between the moving electrons and the vibrating atoms. These collisions impede the flow of electrons, increasing the resistance.
The increased atomic vibrations also result in more collisions between the electrons and the atoms. These collisions scatter the electrons, making it more difficult for them to move through the material. Consequently, the resistance of the material increases.
At higher temperatures, the electron mobility, which is the ability of electrons to move freely in a material, decreases. This decrease in electron mobility further contributes to the increase in resistance.
There are a few materials, such as certain semiconductors and superconductors, that exhibit a negative temperature coefficient of resistance. In these materials, the resistance decreases with an increase in temperature.
In the case of alloys, which are typically metallic substances composed of two or more elements, the resistance increases with temperature due to the increased atomic vibrations, electron-atom collisions, and reduced electron mobility. This phenomenon is important to consider in various applications, such as electrical circuits and devices, where temperature changes can affect the overall performance and efficiency.
Explanation:
When an electric current flows through a material, it encounters resistance, which is the opposition to the flow of electric charge. The resistance of a material depends on various factors, including temperature.
Effect of Temperature on Resistance:
The resistance of most materials, including metals and alloys, increases with an increase in temperature. This phenomenon is referred to as the positive temperature coefficient of resistance.
Factors contributing to the increase in resistance with temperature:
1. Atomic Vibrations:
As the temperature of a material increases, the atoms or ions in the material gain thermal energy and start vibrating more vigorously. This increased atomic vibration leads to more frequent collisions between the moving electrons and the vibrating atoms. These collisions impede the flow of electrons, increasing the resistance.
2. Electron-Atom Collisions:
The increased atomic vibrations also result in more collisions between the electrons and the atoms. These collisions scatter the electrons, making it more difficult for them to move through the material. Consequently, the resistance of the material increases.
3. Changes in Electron Mobility:
At higher temperatures, the electron mobility, which is the ability of electrons to move freely in a material, decreases. This decrease in electron mobility further contributes to the increase in resistance.
Exceptions:
There are a few materials, such as certain semiconductors and superconductors, that exhibit a negative temperature coefficient of resistance. In these materials, the resistance decreases with an increase in temperature.
Conclusion:
In the case of alloys, which are typically metallic substances composed of two or more elements, the resistance increases with temperature due to the increased atomic vibrations, electron-atom collisions, and reduced electron mobility. This phenomenon is important to consider in various applications, such as electrical circuits and devices, where temperature changes can affect the overall performance and efficiency.
Two light bulbs P and Q are identical in all respects, except that P’s filament is thicker than Q’s. If the same potential difference is applied to each, then- a)P will burn brighter because it has the lower resistance
- b)Q will burn brighter because it has the lower resistance.
- c)Q will burn brighter because it has the greater resistance.
- d)P will burn brighter because it has the greater resistance.
Correct answer is 'A'. Can you explain this answer?
Two light bulbs P and Q are identical in all respects, except that P’s filament is thicker than Q’s. If the same potential difference is applied to each, then
a)
P will burn brighter because it has the lower resistance
b)
Q will burn brighter because it has the lower resistance.
c)
Q will burn brighter because it has the greater resistance.
d)
P will burn brighter because it has the greater resistance.
| | Divyansh Mehta answered |
Explanation:
When the same potential difference is applied to two light bulbs, the bulb with lower resistance will draw more current and dissipate more power, causing it to shine brighter.
The resistance of a conductor is directly proportional to its length and inversely proportional to its cross-sectional area. Therefore, thicker filaments have lower resistance than thinner filaments.
Reasoning:
P has a thicker filament than Q, which means it has a lower resistance. Therefore, P will draw more current and dissipate more power than Q, causing it to shine brighter.
Q has a thinner filament than P, which means it has a higher resistance. Therefore, Q will draw less current and dissipate less power than P, causing it to shine dimmer.
Answer:
Hence, the correct answer is option A, which states that P will burn brighter because it has the lower resistance.
When the same potential difference is applied to two light bulbs, the bulb with lower resistance will draw more current and dissipate more power, causing it to shine brighter.
The resistance of a conductor is directly proportional to its length and inversely proportional to its cross-sectional area. Therefore, thicker filaments have lower resistance than thinner filaments.
Reasoning:
P has a thicker filament than Q, which means it has a lower resistance. Therefore, P will draw more current and dissipate more power than Q, causing it to shine brighter.
Q has a thinner filament than P, which means it has a higher resistance. Therefore, Q will draw less current and dissipate less power than P, causing it to shine dimmer.
Answer:
Hence, the correct answer is option A, which states that P will burn brighter because it has the lower resistance.
If R1 and R2 be the resistance of the filament of 40 W and 60 W respectively operating 220 V, then- a)R1 < R2
- b)R2 < R1
- c)R1 = R2
- d)R1 ≥ R2
Correct answer is option 'B'. Can you explain this answer?
If R1 and R2 be the resistance of the filament of 40 W and 60 W respectively operating 220 V, then
a)
R1 < R2
b)
R2 < R1
c)
R1 = R2
d)
R1 ≥ R2
| | Ritu Saxena answered |
Using power,
For the same voltage, R ∝ 1/P
More the power, lesser the resistance.
Accordingly, R2 < R1
For the same voltage, R ∝ 1/P
More the power, lesser the resistance.
Accordingly, R2 < R1
Resistivity of a given conductor depends on- a)length of conductor
- b)length as well as cross-section area of conductor
- c)material and dimensions, of conductor
- d)material of conductor and temperature
Correct answer is option 'D'. Can you explain this answer?
Resistivity of a given conductor depends on
a)
length of conductor
b)
length as well as cross-section area of conductor
c)
material and dimensions, of conductor
d)
material of conductor and temperature
| | Krishna Iyer answered |
Resistivity of a given conductor depends only on its material and the temperature. Resistivity does not depend on the dimensions of the conductor.
Commercial unit of electric energy is- a)volt
- b)joule
- c)watt
- d)Kilowatt-hour
Correct answer is option 'D'. Can you explain this answer?
Commercial unit of electric energy is
a)
volt
b)
joule
c)
watt
d)
Kilowatt-hour
 | Surbhi Gupta answered |
The commercial unit of electrical energy is kilowatt hour.
An electric bulb is marked 18watt-240 volt. If it is used across 240 V power line for one hour daily, calculate the number of days to consume 1 unit of electric energy.- a)54.5 days
- b)57.5 days
- c)50.5 days
- d)55.5 days
Correct answer is 'D'. Can you explain this answer?
An electric bulb is marked 18watt-240 volt. If it is used across 240 V power line for one hour daily, calculate the number of days to consume 1 unit of electric energy.
a)
54.5 days
b)
57.5 days
c)
50.5 days
d)
55.5 days
 | Anjana Bajaj answered |
Let n be the number of days
Here, work done is 36 x 105 J = (18 J/s) x n x 1 x 60 x 60
Thus, n = 55.5 days
Which of the following terms does not represent electrical power in a circuit?- a)V2/R
- b)I2R
- c)IR2
- d)VI
Correct answer is option 'C'. Can you explain this answer?
Which of the following terms does not represent electrical power in a circuit?
a)
V2/R
b)
I2R
c)
IR2
d)
VI
| | Nisha Choudhury answered |
Electric power in terms of current = IR2 and in terms of voltage = V2/R and in terms of voltage and current both = VI
Three resistors of 1Ω, 2 Ω and 3 Ω are connected in series with a battery of 12 V as shown in figure. Values of potential differences V1, V2, V3 across the three resistors have respective values :- a)2 V, 4 V, 6 V
- b)6 V, 4 V, 2 V
- c)3 V , 2 V , 1 V
- d)
Correct answer is option 'A'. Can you explain this answer?
Three resistors of 1Ω, 2 Ω and 3 Ω are connected in series with a battery of 12 V as shown in figure. Values of potential differences V1, V2, V3 across the three resistors have respective values :
a)
2 V, 4 V, 6 V
b)
6 V, 4 V, 2 V
c)
3 V , 2 V , 1 V
d)
 | Vp Classes answered |
In series grouping current I is same throughout and potential differences are directly proportional to respective resistances.
In given circuit
∴ V1 = IR1 = 2 A x 1Ω = 2V,
In given circuit
∴ V1 = IR1 = 2 A x 1Ω = 2V,
V2 = IR2 = 2 A x 2 Ω = 4 V and
V3 = IR3 = 2 A x 3 Ω = 6 V.
Which alloy is used to prepare the heating element of an electric iron ?- a)Constanton
- b)Tin-lead alloy
- c)German silver
- d)Nichrome
Correct answer is option 'D'. Can you explain this answer?
Which alloy is used to prepare the heating element of an electric iron ?
a)
Constanton
b)
Tin-lead alloy
c)
German silver
d)
Nichrome
| | Amit Sharma answered |
An alloy ‘nichrome’ is used to prepare the heating element of an electric iron because its resistivity is high, its melting point is high and it does not oxidise easily.
The graph between current I and potential difference V in the experimental verification of Ohm’s law were drawn by four students. Which one is correct ?- a)
- b)
- c)
- d)
Correct answer is option 'B'. Can you explain this answer?
The graph between current I and potential difference V in the experimental verification of Ohm’s law were drawn by four students. Which one is correct ?
a)
b)
c)
d)
 | Kshitij rane answered |
I-V graph shown in figure (b) is correct because I ∝ 7.
The symbol used for representing Independent sources- a)Diamond
- b)Square
- c)Circle
- d)Triangle
Correct answer is option 'C'. Can you explain this answer?
The symbol used for representing Independent sources
a)
Diamond
b)
Square
c)
Circle
d)
Triangle
| | Amit Sharma answered |
Independent sources are represented by circle
Dependent sources are represented by Diamond.
Dependent sources are represented by Diamond.
Two light bulbs are marked 230 V; 75 W and 230 V; 150 W. If the first bulb has a resistance R, then the resistance of the second is;- a)2R
- b)(1/2)R
- c)4R
- d)(1/4) R
Correct answer is option 'B'. Can you explain this answer?
Two light bulbs are marked 230 V; 75 W and 230 V; 150 W. If the first bulb has a resistance R, then the resistance of the second is;
a)
2R
b)
(1/2)R
c)
4R
d)
(1/4) R
| | Pooja Shah answered |
Power = voltage * current
= Voltage * ( voltage / resistance)
Hence, if P is power, V is Voltage and R is resistance, then R = V ^2/ R
Hence for first bulb, R1 = V^2/75 = R
For second bulb, R2 = V^2 / 150
= > ½ (V^2/75) = R/2
=> R/2
= Voltage * ( voltage / resistance)
Hence, if P is power, V is Voltage and R is resistance, then R = V ^2/ R
Hence for first bulb, R1 = V^2/75 = R
For second bulb, R2 = V^2 / 150
= > ½ (V^2/75) = R/2
=> R/2
Can you explain the answer of this question below:Two bulbs marked 200 watt-250 volts and 100 watt-250 volts are joined in series to 250 volts supply. Power consumed in circuit is- A:67 watt
- B:100 watt
- C:300 watt
- D:33 watt
The answer is a.
Two bulbs marked 200 watt-250 volts and 100 watt-250 volts are joined in series to 250 volts supply. Power consumed in circuit is
A:
67 watt
B:
100 watt
C:
300 watt
D:
33 watt
| | Rajiv Gupta answered |
We know that, R = V^2 /P
Hence resistance of 1st bulb = (250)^2 / 200 = 625/2
resistance of 2nd bulb = (250)^2 / 100 = 625
Total resistance of the circuit when the bulbs are connceted in series = 625/2 + 625 = 1875/2 ohm
Therefore, total power consumed in the circuit , P = (250)^2 / (1875/2) = 67 watt
A bulb is rated as 270V, 0.5 A. Its power is- a)125 watt
- b)100 watt
- c)60 watt
- d)135 watt
Correct answer is option 'D'. Can you explain this answer?
A bulb is rated as 270V, 0.5 A. Its power is
a)
125 watt
b)
100 watt
c)
60 watt
d)
135 watt
| | Rahul Kapoor answered |
Voltage (V) = 270 Volts
Current (I) = 0.5 A
Power (P) = V x I
= 270 x 0.5 = 135 watt
The resistance of hot filament of the bulb is about 10 times the cold resistance. What will be the resistance of 100 W-220 V lamp, when not in use ?- a)48Ω
- b)400Ω
- c)484Ω
- d)48.4Ω
Correct answer is option 'D'. Can you explain this answer?
The resistance of hot filament of the bulb is about 10 times the cold resistance. What will be the resistance of 100 W-220 V lamp, when not in use ?
a)
48Ω
b)
400Ω
c)
484Ω
d)
48.4Ω
| | Amit Kumar answered |
When the lamp is on use, it is hot.
Using joules law of heating ;
P = V2 / R
R = 2202 /100 = 484 ohm.
It is given resistance of hot lamp is 20 times the cold lamp.
Hence, R cold = 484/10 = 48.4 ohm.
Using joules law of heating ;
P = V2 / R
R = 2202 /100 = 484 ohm.
It is given resistance of hot lamp is 20 times the cold lamp.
Hence, R cold = 484/10 = 48.4 ohm.
An electric refrigerator rated 500 W operates 10 hr per day. What is the cost of the energy to operate it for 30 days at Rs. 4.00 per kWh?- a)Rs. 600
- b)Rs. 400
- c)Rs. 500
- d)Rs. 800
Correct answer is option 'A'. Can you explain this answer?
An electric refrigerator rated 500 W operates 10 hr per day. What is the cost of the energy to operate it for 30 days at Rs. 4.00 per kWh?
a)
Rs. 600
b)
Rs. 400
c)
Rs. 500
d)
Rs. 800
| | Gaurav Kumar answered |
The Fuse wire connection are in between the appliance and main line. It is are very thin wire and when very high current passes through it suddenly, the fuse wire gets heated and melts due to the produced heat. This saves the household appliances
What does the straight-line V-I graph indicate about a metallic wire?- a)The resistance of the wire increases with current.
- b)The potential difference is not proportional to the current.
- c)The potential difference increases linearly with current.
- d)The wire does not follow Ohm's Law.
Correct answer is option 'C'. Can you explain this answer?
What does the straight-line V-I graph indicate about a metallic wire?
a)
The resistance of the wire increases with current.
b)
The potential difference is not proportional to the current.
c)
The potential difference increases linearly with current.
d)
The wire does not follow Ohm's Law.
 | Atul kumar answered |
Understanding the V-I Graph of a Metallic Wire
When analyzing the relationship between voltage (V) and current (I) in a metallic wire, a straight-line graph indicates specific electrical properties of the conductor.
Characteristics of the Graph
- A straight-line V-I graph signifies that the relationship between voltage and current is linear.
- This linearity implies that as the current increases, the potential difference (voltage) across the wire also increases proportionally.
Ohm's Law
- The behavior of the wire follows Ohm's Law, which states that V = I * R, where R is the resistance.
- Since the graph is a straight line, it indicates that the resistance (R) remains constant regardless of the current flowing through the wire.
Key Implications
- Constant Resistance: The straight line indicates the wire’s resistance does not change with varying current levels.
- Direct Proportionality: The potential difference increases linearly with the increase in current, which confirms that the wire behaves predictably under electrical conditions.
Conclusion
In summary, the straight-line V-I graph of a metallic wire demonstrates that the potential difference is directly proportional to the current. Thus, option ‘C’ is correct, as it encompasses the essence of the wire's behavior according to Ohm's Law. This property is fundamental in understanding how metallic conductors operate in electrical circuits.
When analyzing the relationship between voltage (V) and current (I) in a metallic wire, a straight-line graph indicates specific electrical properties of the conductor.
Characteristics of the Graph
- A straight-line V-I graph signifies that the relationship between voltage and current is linear.
- This linearity implies that as the current increases, the potential difference (voltage) across the wire also increases proportionally.
Ohm's Law
- The behavior of the wire follows Ohm's Law, which states that V = I * R, where R is the resistance.
- Since the graph is a straight line, it indicates that the resistance (R) remains constant regardless of the current flowing through the wire.
Key Implications
- Constant Resistance: The straight line indicates the wire’s resistance does not change with varying current levels.
- Direct Proportionality: The potential difference increases linearly with the increase in current, which confirms that the wire behaves predictably under electrical conditions.
Conclusion
In summary, the straight-line V-I graph of a metallic wire demonstrates that the potential difference is directly proportional to the current. Thus, option ‘C’ is correct, as it encompasses the essence of the wire's behavior according to Ohm's Law. This property is fundamental in understanding how metallic conductors operate in electrical circuits.
If a wire follows Ohm's Law, what type of graph is obtained when potential difference (V) is plotted against current (I)?- a)A curved line
- b)A straight line passing through the origin
- c)A horizontal line
- d)A vertical line
Correct answer is option 'B'. Can you explain this answer?
If a wire follows Ohm's Law, what type of graph is obtained when potential difference (V) is plotted against current (I)?
a)
A curved line
b)
A straight line passing through the origin
c)
A horizontal line
d)
A vertical line
 | Gowri Mehta answered |
Understanding Ohm's Law
Ohm's Law states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points, provided the temperature remains constant. Mathematically, it is expressed as:
V = I * R
where R is the resistance.
Graphical Representation
When you plot the potential difference (V) against the current (I):
- Type of Graph: The graph results in a straight line.
Key Points about the Graph
- Straight Line: The linear nature indicates that as current increases, voltage also increases proportionally.
- Passes Through the Origin: The straight line intersects the origin (0,0). This signifies that when there is no current (I=0), there is also no voltage (V=0).
- Slope Represents Resistance: The slope of the line represents the resistance (R) of the wire. A steeper slope indicates higher resistance.
Conclusion
The straight line passing through the origin confirms that the wire obeys Ohm's Law, demonstrating a consistent relationship between voltage and current. Thus, option 'B' is indeed the correct answer.
Ohm's Law states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points, provided the temperature remains constant. Mathematically, it is expressed as:
V = I * R
where R is the resistance.
Graphical Representation
When you plot the potential difference (V) against the current (I):
- Type of Graph: The graph results in a straight line.
Key Points about the Graph
- Straight Line: The linear nature indicates that as current increases, voltage also increases proportionally.
- Passes Through the Origin: The straight line intersects the origin (0,0). This signifies that when there is no current (I=0), there is also no voltage (V=0).
- Slope Represents Resistance: The slope of the line represents the resistance (R) of the wire. A steeper slope indicates higher resistance.
Conclusion
The straight line passing through the origin confirms that the wire obeys Ohm's Law, demonstrating a consistent relationship between voltage and current. Thus, option 'B' is indeed the correct answer.
Two Wires of same length and area, made of two materials of resistivity ρ1 and ρ2 are connected in parallel V to a source of potential. The equivalent resistivity for the same length and area is- a)ρ1 + ρ2
- b)(ρ1.ρ2) / (ρ1 + ρ2)
- c)(2.ρ1.ρ2) / (ρ1 + ρ2)
- d)|ρ1 - ρ2|
Correct answer is option 'B'. Can you explain this answer?
Two Wires of same length and area, made of two materials of resistivity ρ1 and ρ2 are connected in parallel V to a source of potential. The equivalent resistivity for the same length and area is
a)
ρ1 + ρ2
b)
(ρ1.ρ2) / (ρ1 + ρ2)
c)
(2.ρ1.ρ2) / (ρ1 + ρ2)
d)
|ρ1 - ρ2|
 | Tanishq Chauhan answered |
Understanding Parallel Resistance
When two resistors (or wires in this case) are connected in parallel, the total (or equivalent) resistance can be determined using a specific formula. This is crucial for understanding how resistivity works in parallel circuits.
Resistivity of Wires
- Each wire has its own resistivity: ρ1 and ρ2.
- Both wires are of the same length (L) and cross-sectional area (A).
Formula for Equivalent Resistance
For resistors in parallel, the formula to find the equivalent resistance (R_eq) is given by:
1/R_eq = 1/R1 + 1/R2
Where R1 and R2 are the resistances of the individual wires. Since resistance (R) can be expressed in terms of resistivity (ρ):
R = ρL/A
Deriving the Equivalent Resistance
1. Calculate the resistance of each wire:
- R1 = ρ1 * (L/A)
- R2 = ρ2 * (L/A)
2. Substitute these into the parallel resistance formula:
- 1/R_eq = A/(ρ1*L) + A/(ρ2*L)
3. Simplifying this gives:
- 1/R_eq = (A/L) * (1/ρ1 + 1/ρ2)
4. Finding R_eq leads to:
- R_eq = (ρ1 * ρ2) / (ρ1 + ρ2) * (L/A)
Equivalent Resistivity
Thus, the equivalent resistivity for the two wires connected in parallel is:
ρ_eq = (ρ1 * ρ2) / (ρ1 + ρ2)
This shows that the correct answer is option 'B', which confirms the behavior of resistors in parallel.
Conclusion
Understanding how resistivity combines in a parallel circuit is essential for analyzing electrical systems, and option B accurately represents the equivalent resistivity of two parallel wires made from different materials.
When two resistors (or wires in this case) are connected in parallel, the total (or equivalent) resistance can be determined using a specific formula. This is crucial for understanding how resistivity works in parallel circuits.
Resistivity of Wires
- Each wire has its own resistivity: ρ1 and ρ2.
- Both wires are of the same length (L) and cross-sectional area (A).
Formula for Equivalent Resistance
For resistors in parallel, the formula to find the equivalent resistance (R_eq) is given by:
1/R_eq = 1/R1 + 1/R2
Where R1 and R2 are the resistances of the individual wires. Since resistance (R) can be expressed in terms of resistivity (ρ):
R = ρL/A
Deriving the Equivalent Resistance
1. Calculate the resistance of each wire:
- R1 = ρ1 * (L/A)
- R2 = ρ2 * (L/A)
2. Substitute these into the parallel resistance formula:
- 1/R_eq = A/(ρ1*L) + A/(ρ2*L)
3. Simplifying this gives:
- 1/R_eq = (A/L) * (1/ρ1 + 1/ρ2)
4. Finding R_eq leads to:
- R_eq = (ρ1 * ρ2) / (ρ1 + ρ2) * (L/A)
Equivalent Resistivity
Thus, the equivalent resistivity for the two wires connected in parallel is:
ρ_eq = (ρ1 * ρ2) / (ρ1 + ρ2)
This shows that the correct answer is option 'B', which confirms the behavior of resistors in parallel.
Conclusion
Understanding how resistivity combines in a parallel circuit is essential for analyzing electrical systems, and option B accurately represents the equivalent resistivity of two parallel wires made from different materials.
Which factor must remain constant for Ohm's Law to be valid?- a)Voltage
- b)Current
- c)Temperature
- d)Resistance
Correct answer is option 'C'. Can you explain this answer?
Which factor must remain constant for Ohm's Law to be valid?
a)
Voltage
b)
Current
c)
Temperature
d)
Resistance
| | Gowri Mehta answered |
Understanding Ohm's Law
Ohm’s Law is a fundamental principle in electrical engineering and physics, stating that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. The relationship is expressed as:
I = V/R
To ensure the validity of Ohm's Law, certain conditions must be maintained.
Constant Temperature
- Resistance Variation: Resistance is influenced by temperature. As temperature increases, the resistance of most conductors also increases, leading to a deviation from Ohm's Law. Therefore, for Ohm's Law to hold true, resistance must remain constant, which is generally achieved by maintaining a constant temperature.
- Material Properties: Different materials exhibit different resistive properties at varying temperatures. For example, metals typically exhibit increased resistance with rising temperatures, while semiconductors may behave differently.
- Practical Implications: In practical circuits, if the temperature changes significantly, the resistance may vary, thus affecting the current for a given voltage. This is particularly important in electronic devices and circuits where temperature control is essential for performance.
Other Factors
- Voltage (a): While voltage can vary, Ohm's Law still applies as long as the other conditions are met.
- Current (b): Similar to voltage, current can change; it is the result of the interplay between voltage and resistance.
- Resistance (d): Resistance can vary based on the material and dimensions of the conductor, but for Ohm’s Law to be valid, it must remain constant, which is primarily controlled by temperature.
In conclusion, the constant temperature ensures that resistance remains unchanged, making Ohm's Law applicable.
Ohm’s Law is a fundamental principle in electrical engineering and physics, stating that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. The relationship is expressed as:
I = V/R
To ensure the validity of Ohm's Law, certain conditions must be maintained.
Constant Temperature
- Resistance Variation: Resistance is influenced by temperature. As temperature increases, the resistance of most conductors also increases, leading to a deviation from Ohm's Law. Therefore, for Ohm's Law to hold true, resistance must remain constant, which is generally achieved by maintaining a constant temperature.
- Material Properties: Different materials exhibit different resistive properties at varying temperatures. For example, metals typically exhibit increased resistance with rising temperatures, while semiconductors may behave differently.
- Practical Implications: In practical circuits, if the temperature changes significantly, the resistance may vary, thus affecting the current for a given voltage. This is particularly important in electronic devices and circuits where temperature control is essential for performance.
Other Factors
- Voltage (a): While voltage can vary, Ohm's Law still applies as long as the other conditions are met.
- Current (b): Similar to voltage, current can change; it is the result of the interplay between voltage and resistance.
- Resistance (d): Resistance can vary based on the material and dimensions of the conductor, but for Ohm’s Law to be valid, it must remain constant, which is primarily controlled by temperature.
In conclusion, the constant temperature ensures that resistance remains unchanged, making Ohm's Law applicable.
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