All Exams >
ACT >
Physics for ACT >
All Questions
All questions of Current Electricity for ACT Exam
The current in a coil of resistance 90 ohms is to be reduced by 90 percent. What value of resistance should be connected in parallel with it?- a)100Ω
- b)10Ω
- c)9Ω
- d)90Ω
Correct answer is option 'B'. Can you explain this answer?
The current in a coil of resistance 90 ohms is to be reduced by 90 percent. What value of resistance should be connected in parallel with it?
a)
100Ω
b)
10Ω
c)
9Ω
d)
90Ω
|
Anjana Sharma answered |
The resistance is connected in parallel. Hence, voltage across the required resistance S and 90Ω is the same, i.e.
0.9 I x S = 0.1 I x 90
S = 90/9= 10Ω
A car battery has ________ resistance than a dry cell.- a)same
- b)much lower
- c)slightly greater
- d)much higher
Correct answer is option 'B'. Can you explain this answer?
A car battery has ________ resistance than a dry cell.
a)
same
b)
much lower
c)
slightly greater
d)
much higher
|
Vijay Bansal answered |
Dry cell car batteries consist of a fiberglass mat that contains electrolytes. The electrolytes cause a chemical reaction that produces electricity. ... Although dry cell car batteries are expensive, they last longer than conventional wet cell batteries. They also have more power to crank the car's engine in bad weather.
A current of 2 ampere is passing through a metallic wire of cross-sectional area 2 x 10-6 m2. If the density of the charge carriers in the wire is 5 x 1026 m-3, then the drift velocity of the electrons will be- a)1.15 x 10-6 m/s
- b)1.5 x 10-5 m/s
- c)1.25 x 10-2 m/s
- d)1.05 x 10-3 m/s
Correct answer is option 'C'. Can you explain this answer?
A current of 2 ampere is passing through a metallic wire of cross-sectional area 2 x 10-6 m2. If the density of the charge carriers in the wire is 5 x 1026 m-3, then the drift velocity of the electrons will be
a)
1.15 x 10-6 m/s
b)
1.5 x 10-5 m/s
c)
1.25 x 10-2 m/s
d)
1.05 x 10-3 m/s
|
Preeti Khanna answered |
Drift velocity, v=I/nAe
=2/(2x10-6)x(5x1026)x(1.6x10-19)
=1.25x10-2m/s
=2/(2x10-6)x(5x1026)x(1.6x10-19)
=1.25x10-2m/s
- a)
- b)
- c)
- d)
Correct answer is 'C'. Can you explain this answer?
|
Mira Joshi answered |
F=-eE .
we know that,
F= ma ,
then
a=F/m.
a=-eE/m.
we know that,
F= ma ,
then
a=F/m.
a=-eE/m.
If cells are joined in parallel, they have _______.- a)same current
- b)same emf
- c)same potential difference
- d)same internal resistance
Correct answer is option 'C'. Can you explain this answer?
If cells are joined in parallel, they have _______.
a)
same current
b)
same emf
c)
same potential difference
d)
same internal resistance
|
Hansa Sharma answered |
Components connected in parallel provide alternative pathways for current flow. When cells are connected in parallel, the total voltages that they provide does not change. For example, when two or more 2 V cells are connected in parallel, they still provide a total voltage of 2 V.
What is the maximum current that can be drawn from a cell of emf E and internal resistance r connected to an external resistance R?- a)I = E/(R+r)
- b)infinite
- c)I = E/R
- d)I = E/r
Correct answer is option 'D'. Can you explain this answer?
What is the maximum current that can be drawn from a cell of emf E and internal resistance r connected to an external resistance R?
a)
I = E/(R+r)
b)
infinite
c)
I = E/R
d)
I = E/r
|
|
Preeti Iyer answered |
as the maximum current that can be drawn from a cell is for R =0 therefore, it is I = E/r.
Three resistors of 4Ω, 12Ω , and 6Ω are connected in parallel. No. of 12Ω resistors required to be connected in parallel to reduce the total resistance to half of its original is- a)6
- b)3
- c)12
- d)2
Correct answer is 'A'. Can you explain this answer?
Three resistors of 4Ω, 12Ω , and 6Ω are connected in parallel. No. of 12Ω resistors required to be connected in parallel to reduce the total resistance to half of its original is
a)
6
b)
3
c)
12
d)
2
|
Riya Banerjee answered |
Here 4 Ω, 12 Ω, 6 Ω when connected in parallel results in 2Ω. to reduce it to half we have to join 1\R original = 6\12 for reducing it to half we have to join 6 , 12 Ω resistors in parallel (6\12) + (1\ 12 × 6) = 12\12 = 1 ohm . Half of its original value therefore option a is correct.
When Wheatstone bridge is in balance condition, the current through galvanometer will be- a)Zero
- b)Maximum
- c)Minimum
- d)Depends upon the type of galvanometer
Correct answer is option 'A'. Can you explain this answer?
When Wheatstone bridge is in balance condition, the current through galvanometer will be
a)
Zero
b)
Maximum
c)
Minimum
d)
Depends upon the type of galvanometer
|
Krishna Iyer answered |
The bridge is said to be balanced when deflection in galvanometer is zero(Ig=0), i.e., no current flows through the galvanometer(branch BD).In the balanced condition,
P/Q=R/S
On mutually changing the position of the cell and galvanometer, this condition will not change.
When the position of cell and galvanometer in a Wheatstone bridge is inter-changed, its balanced condition- a)Changes and depends on galvanometer position only
- b)Changes
- c)Changes and it depends on cell position only
- d)Remains unchanged
Correct answer is option 'D'. Can you explain this answer?
When the position of cell and galvanometer in a Wheatstone bridge is inter-changed, its balanced condition
a)
Changes and depends on galvanometer position only
b)
Changes
c)
Changes and it depends on cell position only
d)
Remains unchanged
|
|
Krishna Iyer answered |
For balanced Wheatstone bridge which is shown in figure a, P/Q=S/R
If we interchange the cell and galvanometer then circuit becomes as shown in figure b.
and balanced condition, P/S=Q/R⇒P/Q=S/R
Thus, balanced point remains unchanged.
If we interchange the cell and galvanometer then circuit becomes as shown in figure b.
and balanced condition, P/S=Q/R⇒P/Q=S/R
Thus, balanced point remains unchanged.
Under what condition, the current drawn from the cell is maximum?- a)R = r
- b)R > r
- c)R = 0
- d)R < r
Correct answer is option 'C'. Can you explain this answer?
Under what condition, the current drawn from the cell is maximum?
a)
R = r
b)
R > r
c)
R = 0
d)
R < r
|
|
Ritu Singh answered |
The maximum current can be drawn from a cell if the external resistance R = 0.
When current is to be drawn at max then the conducting wire rating comes high such that resistance is less.
Resistance R = rho x l/a
Rho = resistivity constant
L=length
a=area of cross-section
Hence, if the area of cross-section increases resistance decreases by increasing the rate of current to flow.
Two cells of 1.25 V and 0.75V are connected in parallel. The effective voltage will be- a)0.5 V
- b)2.00 V
- c)1.25 V
- d)0.75 V
Correct answer is option 'A'. Can you explain this answer?
Two cells of 1.25 V and 0.75V are connected in parallel. The effective voltage will be
a)
0.5 V
b)
2.00 V
c)
1.25 V
d)
0.75 V
|
|
Anjana Sharma answered |
When two cells are conneted in parallel , then
Effective Voltage,V = V1 − V2 = 1.25 − 0.75 = 0.5 V
Specific resistance of a conductor increases with- a)Increase in cross-section and decrease in length
- b)Increase in cross-section
- c)Decrease in cross-section
- d)Increase in temperature
Correct answer is option 'D'. Can you explain this answer?
Specific resistance of a conductor increases with
a)
Increase in cross-section and decrease in length
b)
Increase in cross-section
c)
Decrease in cross-section
d)
Increase in temperature
|
|
Anjana Sharma answered |
Therefore resistance increases with the length. When cross sectional area increases the space of the elctrons to travel increases(simply explained). Therefore less amount of obstacles for the current. Therefore when area increases the resistance decreases.
Five resistances are connected as shown in fig. The effective resistance between points A and B is
- a)20/30Ω
- b)15Ω
- c)10/3Ω
- d)6Ω
Correct answer is option 'C'. Can you explain this answer?
Five resistances are connected as shown in fig. The effective resistance between points A and B is
a)
20/30Ω
b)
15Ω
c)
10/3Ω
d)
6Ω
|
Lekshmi Basu answered |
The given circuit is a balanced Wheatstone bridge type, hence it can be simplified 
At any junction, the sum of the currents entering the junction is equal to the sum of _______- a)potential around any closed loop
- b)voltages across the junction
- c)all the currents in the circuit
- d)currents leaving the junction
Correct answer is option 'D'. Can you explain this answer?
At any junction, the sum of the currents entering the junction is equal to the sum of _______
a)
potential around any closed loop
b)
voltages across the junction
c)
all the currents in the circuit
d)
currents leaving the junction
|
Om Kumar answered |
The correct answer is option 'D': currents leaving the junction.
Explanation:
At any junction in an electrical circuit, the sum of the currents entering the junction is equal to the sum of the currents leaving the junction. This is based on the principle of conservation of charge.
When current flows through a junction, it must split into multiple paths. The total amount of charge entering the junction must be equal to the total amount of charge leaving the junction. This is because charge cannot be created or destroyed, it can only flow through the circuit.
To better understand this concept, consider a simple circuit with three branches connected to a junction. Let's label the currents entering the junction as I1, I2, and I3, and the currents leaving the junction as I4, I5, and I6.
The principle of conservation of charge states that the total amount of charge entering the junction must be equal to the total amount of charge leaving the junction. Mathematically, this can be expressed as:
I1 + I2 + I3 = I4 + I5 + I6
This equation shows that the sum of the currents entering the junction (I1 + I2 + I3) is equal to the sum of the currents leaving the junction (I4 + I5 + I6).
This principle is a consequence of Kirchhoff's current law (KCL), which states that the algebraic sum of currents at any junction in an electrical circuit is zero. This means that the sum of currents entering the junction is equal to the sum of currents leaving the junction.
In summary, at any junction in an electrical circuit, the sum of the currents entering the junction is equal to the sum of the currents leaving the junction. This principle is based on the conservation of charge and is a consequence of Kirchhoff's current law.
Explanation:
At any junction in an electrical circuit, the sum of the currents entering the junction is equal to the sum of the currents leaving the junction. This is based on the principle of conservation of charge.
When current flows through a junction, it must split into multiple paths. The total amount of charge entering the junction must be equal to the total amount of charge leaving the junction. This is because charge cannot be created or destroyed, it can only flow through the circuit.
To better understand this concept, consider a simple circuit with three branches connected to a junction. Let's label the currents entering the junction as I1, I2, and I3, and the currents leaving the junction as I4, I5, and I6.
The principle of conservation of charge states that the total amount of charge entering the junction must be equal to the total amount of charge leaving the junction. Mathematically, this can be expressed as:
I1 + I2 + I3 = I4 + I5 + I6
This equation shows that the sum of the currents entering the junction (I1 + I2 + I3) is equal to the sum of the currents leaving the junction (I4 + I5 + I6).
This principle is a consequence of Kirchhoff's current law (KCL), which states that the algebraic sum of currents at any junction in an electrical circuit is zero. This means that the sum of currents entering the junction is equal to the sum of currents leaving the junction.
In summary, at any junction in an electrical circuit, the sum of the currents entering the junction is equal to the sum of the currents leaving the junction. This principle is based on the conservation of charge and is a consequence of Kirchhoff's current law.
If the potential difference V applied on a conductor is doubled, the drift velocity of electrons will become- a)vd
- b)2vd
- c)4vd
- d)
Correct answer is option 'B'. Can you explain this answer?
If the potential difference V applied on a conductor is doubled, the drift velocity of electrons will become
a)
vd
b)
2vd
c)
4vd
d)
|
Suresh Iyer answered |
Drift velocity is directly proportional to potential difference.
Drift velocity is defined as the average velocity with which free electrons get drifted towards the positive end of the conductor under the influence of an external electric field.
Drift velocity is given by
vd= eEτ/ m
But, E=V/l
(if l is length of the conductor and V is constant potential difference applied across the ends of the conductor)
∴vd= eVτ/ml
⇒vd∝V
So, when the potential difference is doubled the drift velocity will be doubled.
Note - Current flowing through a conductor is directly proportional to the drift velocity.
Drift velocity is defined as the average velocity with which free electrons get drifted towards the positive end of the conductor under the influence of an external electric field.
Drift velocity is given by
vd= eEτ/ m
But, E=V/l
(if l is length of the conductor and V is constant potential difference applied across the ends of the conductor)
∴vd= eVτ/ml
⇒vd∝V
So, when the potential difference is doubled the drift velocity will be doubled.
Note - Current flowing through a conductor is directly proportional to the drift velocity.
emf is measured in- a)J.C
- b)J
- c)J/C
- d)J/C/m
Correct answer is option 'C'. Can you explain this answer?
emf is measured in
a)
J.C
b)
J
c)
J/C
d)
J/C/m
|
|
Rohan Singh answered |
Electromotive force, abbreviated emf (denoted and measured in volts), is the electrical intensity or "pressure" developed by a source of electrical energy such as a battery or generator. ... This potential difference can drive an electric current if an external circuit is attached to the terminals. It is commonly measured in units of volts, equivalent in the metre–kilogram–second system to one joule per coulomb of electric charge. In the electrostatic units of the centimetre–gram–second system, the unit of electromotive force is the statvolt, or one erg per electrostatic unit of charge.
- a)1 ohm
- b)0.5 ohm
- c)1.5 ohm
- d)2 ohm
Correct answer is 'A'. Can you explain this answer?
|
|
Preeti Iyer answered |
let the resistance of the two cells be 'r'
now,
when joined in series
RS = r + r + 1
or
RS = 2r + 1
the series current in this case would be
IS= V/R = 2E/RS
[V = E + E - total emf]
or
IS = 2E / (2r + 1)
and
when joined in parallel
1/RP = (1/r) + (1/r) + 1
or
RP = 1 + r/2
the parallel current in this case would be
IP = V/RP = E/RP
or
IP = E / (1 + r/2)
now,
we are given
IS = IP
so,
2E / (2r + 1) = E / (1 + r/2)
or
2 + r = 2r + 1
thus,
r = 1 ohm
- a)0.75 A
- b)1.05 A
- c)2 A
- d)3 A
Correct answer is 'A'. Can you explain this answer?
|
|
Rohan Singh answered |
Total inner voltage E = 2*3 = 6.0 V
Total resist. Rt = 0.2*3*7.4 = 8.0 ohm
circulating current I = E/Rt = 6/8 = 3/4 = 0.75 A
The Wheatstone bridge Principle is deduced using- a)Gauss’s Law
- b)Kirchhoff’s Laws
- c)Coulomb’s Law
- d)Newton’s Laws
Correct answer is option 'B'. Can you explain this answer?
The Wheatstone bridge Principle is deduced using
a)
Gauss’s Law
b)
Kirchhoff’s Laws
c)
Coulomb’s Law
d)
Newton’s Laws
|
|
Anjana Sharma answered |
PRINCIPLE: Wheatstone bridge principle states that when the bridge is balanced, the product of the resistance of the opposite arms are equal. The files that I had attached in which I had derived Wheatstone bridge equation using Kirchhoff law is useful to you.
- a)yes
- b)No
- c)Can’t predict
- d)None of the above
Correct answer is 'A'. Can you explain this answer?
|
Vaishnavi Nayak answered |
In series connection of cells total internal resistance=nr total resistance of circuit=nR current is same potential difference is different so,I=nv/nR+nr I=V/R+r current is same as before in parallel connection of cells total internal resistance=r/n total resistance of circuit=R/n total current=nI potential difference is same nI=V/r/n+R/n I=V/R+r current is same as before
Can you explain the answer of this question below:The ______ of changes in potential around any closed loop involving resistors and cells in a loop is zero.- A:product
- B:algebraic sum
- C:difference
- D:sum of absolute values
The answer is b.
The ______ of changes in potential around any closed loop involving resistors and cells in a loop is zero.
A:
product
B:
algebraic sum
C:
difference
D:
sum of absolute values
|
Lavanya Menon answered |
In accordance with Kirchhoff’s second law i.e. Kirchhoff’s voltage law (KVL), the algebraic sum of all the potential differences in a closed electric circuit or closed loop that contains one or more cells and resistors is always equal to zero.
This law is popularly called the law of conservation of voltage.
This law is popularly called the law of conservation of voltage.
In a meter bridge experiment a balance point is obtained at a distance of 60 cm from the left end when unknown resistance R is in a left gap and 8 ohms resistor is connected in the right gap. When the position of R and 8 ohm resistor is interchanged the balance point will be at distance of- a)40 cm
- b)30 cm
- c)50 cm
- d)60 cm
Correct answer is option 'A'. Can you explain this answer?
In a meter bridge experiment a balance point is obtained at a distance of 60 cm from the left end when unknown resistance R is in a left gap and 8 ohms resistor is connected in the right gap. When the position of R and 8 ohm resistor is interchanged the balance point will be at distance of
a)
40 cm
b)
30 cm
c)
50 cm
d)
60 cm
|
Jyoti Sengupta answered |
60/40 = l/100-l, = R/8
so R=12
now changed position 8 is proportional to l and 12 to (100-l)
8/12 = l/100-l
l = 40ohm
Can you explain the answer of this question below:What is current I in the circuit as shown in figure?
- A:
1 A
- B:
2.0 A
- C:
1.2 A
- D:
0.5 A
The answer is b.
What is current I in the circuit as shown in figure?
1 A
2.0 A
1.2 A
0.5 A
|
Surya answered |
Yes option B is correct... first u straight the three resistance then it change in series... so u add three u get 6 ohms... after, that 6 ohm is parallel to 3ohm so;3/2.. so as per ohms law;V=IR (since:V=3; R=3/2; I=?) 3=3/2×I I=2ampere... that's it...hope u clear...!!👍😊
- a)0.11 ohm
- b)0 ohm
- c)0. 12 ohm
- d)1.1 ohm
Correct answer is 'B'. Can you explain this answer?
|
|
Rajeev Saxena answered |
Total emf = 3 x 4 = 12 V
Total resistance = 6 + 3r
Current in the circuit = 2 A
Using ohms law
2 = 12/ (6+3r)
2(6+3r)=12
12+6r=12
6r = 12-12 = 0
r = 0/6 = 0
On heating a conductor its resistance- a)depends on type of metal
- b)remains constant
- c)increases
- d)decreases
Correct answer is option 'C'. Can you explain this answer?
On heating a conductor its resistance
a)
depends on type of metal
b)
remains constant
c)
increases
d)
decreases
|
|
Rahul Bansal answered |
The resistance increases as the temperature of a metallic conductor increase, so the resistance is directly proportional to the temperature. When we increase the temperature the amplitude of vibration of atoms increases as a result of which the number of collision among the electrons and atom increases, and hence resistances increases.
Meter Bridge or Slide Wire Bridge is a practical form of- a)Ammeter
- b)Voltmeter
- c)Wheatstone bridge
- d)Potentiometer
Correct answer is option 'C'. Can you explain this answer?
Meter Bridge or Slide Wire Bridge is a practical form of
a)
Ammeter
b)
Voltmeter
c)
Wheatstone bridge
d)
Potentiometer
|
|
Aarav Khanna answered |
Meter Bridge or Slide Wire Bridge is a practical form of Wheatstone bridge.
Wheatstone Bridge:
The Wheatstone bridge is a circuit used to measure unknown resistance by balancing it against a known resistance. It consists of four resistors arranged in a diamond shape, with a galvanometer connected between two opposite corners and a battery connected to the other two corners. When the bridge is balanced, the galvanometer shows zero deflection, indicating that the ratio of the unknown resistance to the known resistance is equal to the ratio of the other two resistors.
Meter Bridge or Slide Wire Bridge:
The meter bridge, also known as the slide wire bridge, is a practical form of the Wheatstone bridge. It consists of a long uniform wire of uniform cross-section called the meter wire, which is stretched over a wooden board. The meter wire is usually made of manganin or constantan, which have low temperature coefficients of resistance.
Construction:
The meter bridge consists of a uniform wire AB, which is connected to a galvanometer G at its midpoint. The wire is divided into two parts by a gap at the center, where a resistance box is connected. A jockey J is used to make contact with the wire and slide along its length.
Working Principle:
To measure an unknown resistance using the meter bridge, the jockey is initially placed at the midpoint of the wire (point O). The resistance box is adjusted until the galvanometer shows zero deflection. At this point, the bridge is in a balanced condition.
The principle behind the working of the meter bridge is that when the bridge is balanced, the ratio of the lengths of the two arms of the wire (AO and OB) is equal to the ratio of the resistances (R1 and R2) in the two arms. Mathematically, this can be represented as:
R1/R2 = AO/OB
By measuring the lengths AO and OB, the ratio R1/R2 can be determined. Since one of the resistances (R1 or R2) is known, the unknown resistance can be calculated.
Advantages of Meter Bridge:
1. High Accuracy: The meter bridge offers high accuracy in measuring resistance as it is based on the principle of a balanced bridge.
2. Simple Construction: The meter bridge is relatively simple in construction and easy to use.
3. Low Cost: The materials required for constructing a meter bridge are easily available and inexpensive.
4. Versatility: The meter bridge can be used to measure a wide range of resistances, making it a versatile instrument.
In conclusion, the meter bridge or slide wire bridge is a practical form of the Wheatstone bridge and is used to measure unknown resistances accurately.
Wheatstone Bridge:
The Wheatstone bridge is a circuit used to measure unknown resistance by balancing it against a known resistance. It consists of four resistors arranged in a diamond shape, with a galvanometer connected between two opposite corners and a battery connected to the other two corners. When the bridge is balanced, the galvanometer shows zero deflection, indicating that the ratio of the unknown resistance to the known resistance is equal to the ratio of the other two resistors.
Meter Bridge or Slide Wire Bridge:
The meter bridge, also known as the slide wire bridge, is a practical form of the Wheatstone bridge. It consists of a long uniform wire of uniform cross-section called the meter wire, which is stretched over a wooden board. The meter wire is usually made of manganin or constantan, which have low temperature coefficients of resistance.
Construction:
The meter bridge consists of a uniform wire AB, which is connected to a galvanometer G at its midpoint. The wire is divided into two parts by a gap at the center, where a resistance box is connected. A jockey J is used to make contact with the wire and slide along its length.
Working Principle:
To measure an unknown resistance using the meter bridge, the jockey is initially placed at the midpoint of the wire (point O). The resistance box is adjusted until the galvanometer shows zero deflection. At this point, the bridge is in a balanced condition.
The principle behind the working of the meter bridge is that when the bridge is balanced, the ratio of the lengths of the two arms of the wire (AO and OB) is equal to the ratio of the resistances (R1 and R2) in the two arms. Mathematically, this can be represented as:
R1/R2 = AO/OB
By measuring the lengths AO and OB, the ratio R1/R2 can be determined. Since one of the resistances (R1 or R2) is known, the unknown resistance can be calculated.
Advantages of Meter Bridge:
1. High Accuracy: The meter bridge offers high accuracy in measuring resistance as it is based on the principle of a balanced bridge.
2. Simple Construction: The meter bridge is relatively simple in construction and easy to use.
3. Low Cost: The materials required for constructing a meter bridge are easily available and inexpensive.
4. Versatility: The meter bridge can be used to measure a wide range of resistances, making it a versatile instrument.
In conclusion, the meter bridge or slide wire bridge is a practical form of the Wheatstone bridge and is used to measure unknown resistances accurately.
A carbon resistor is marked in green, red, and orange bands. The approximate resistance of the resistor is
- a)52 x 103 Ω
- b)25000 Ω
- c)5 x 102 Ω
- d)5 x 104 Ω
Correct answer is option 'A'. Can you explain this answer?
A carbon resistor is marked in green, red, and orange bands. The approximate resistance of the resistor is
a)
52 x 103 Ω
b)
25000 Ω
c)
5 x 102 Ω
d)
5 x 104 Ω
|
|
Anjana Sharma answered |
To determine the resistance of a carbon resistor based on the color bands, we need to refer to the standard resistor color code. The colors represent digits and multipliers as follows:
- Green: 5
- Red: 2
- Orange: Multiplier of 10^3 (1,000)
Given the color bands: Green, Red, Orange
The resistance value is calculated as follows:
- First digit: Green = 5
- Second digit: Red = 2
- Multiplier: Orange = 10^3 (1,000)
So the resistance is:
Resistance=(52)×10^3 ohms=52,000 ohms=52 kilo-ohms
Answer: The approximate resistance of the resistor is 52 kΩ.
The resistance in ohms in the four arms of a Wheatstone bridge are as follows. In which combination of the following is the bridge balanced?
- a)P, R, S, Q
- b)P, R, Q, S
- c)Q, P, R, S
- d)S, R, P, Q
Correct answer is option 'B'. Can you explain this answer?
The resistance in ohms in the four arms of a Wheatstone bridge are as follows. In which combination of the following is the bridge balanced?
a)
P, R, S, Q
b)
P, R, Q, S
c)
Q, P, R, S
d)
S, R, P, Q
|
|
Shreya Singh answered |
Wheat stone bridge follows.P/Q=R/S, condition. b) P=2, Q=3 ,R= 4,S=62/3=4/62/3= 2/3...
A Wheatstone bridge is balanced for four resistors R1, R2, R3 and R4 with a Lech lanche cell between A and C and a galvanometer between B and D. The positions of the cell and the galvanometer are interchanged. The balance will- a)Not change
- b)Change and can be obtained by changing R1
- c)decrease by about 9%9%
- d)Change and can be obtained by changing R4
Correct answer is option 'A'. Can you explain this answer?
A Wheatstone bridge is balanced for four resistors R1, R2, R3 and R4 with a Lech lanche cell between A and C and a galvanometer between B and D. The positions of the cell and the galvanometer are interchanged. The balance will
a)
Not change
b)
Change and can be obtained by changing R1
c)
decrease by about 9%9%
d)
Change and can be obtained by changing R4
|
|
Priyanka Sharma answered |
The balance point will not change . For balancing of wheatstone bridge four arms of resistors are responsible. Interchange the position of galvanometer and cell does not affect balancing of wheatstone bridge.
The unit of current is- a)newton
- b)joule
- c)Ampere
- d)coulomb
Correct answer is option 'C'. Can you explain this answer?
The unit of current is
a)
newton
b)
joule
c)
Ampere
d)
coulomb
|
Nishant Singh answered |
The answer is Ampere because
1. Newton is SI Unit of Force
2.Joule is SI Unit of Work Done
3. Coulomb is SI Unit of Charge
so we can say thay unit if current of Ampere
1. Newton is SI Unit of Force
2.Joule is SI Unit of Work Done
3. Coulomb is SI Unit of Charge
so we can say thay unit if current of Ampere
When number of identical cells, in parallel combination are increased, the voltage of the circuit will- a)Increase
- b)Decrease
- c)Remain same
- d)Depends on the internal resistance of the battery
Correct answer is option 'C'. Can you explain this answer?
When number of identical cells, in parallel combination are increased, the voltage of the circuit will
a)
Increase
b)
Decrease
c)
Remain same
d)
Depends on the internal resistance of the battery
|
|
Lavanya Menon answered |
The voltage developed by the cells in parallel connection cannot be increased by increasing the number of cells present in the circuit. It is because they do not have the same circular path. In parallel connection the connection provides power based on one cell.
The voltage will remain the same.
The voltage will remain the same.
Current provided by a battery is maximum when- a)internal resistance is equal to external resistance
- b)internal resistance is greater then external resistance
- c)internal resistance is less than external resistance
- d)none of these
Correct answer is option 'A'. Can you explain this answer?
Current provided by a battery is maximum when
a)
internal resistance is equal to external resistance
b)
internal resistance is greater then external resistance
c)
internal resistance is less than external resistance
d)
none of these
|
|
Pooja Mehta answered |
Current provided by a battery is maximum when internal resistance is equal to external resistance. As a battery discharges, not only does it diminish its internal store of energy, but its internal resistance also increases (as the electrolyte becomes less and less conductive), and its open-circuit cell voltage decreases (as the chemicals become more and more dilute). The most deceptive change that a discharging battery exhibits is increased resistance.
- a)2.5 ohm
- b)3.2 ohm
- c)2 ohm
- d)4.5 ohm
Correct answer is 'A'. Can you explain this answer?
|
Nikita Singh answered |
The internal resistance of the cell can be obtained from the relation,
I=ε/R+r
0.2=2.5/(10+r)=2.5ohm
I=ε/R+r
0.2=2.5/(10+r)=2.5ohm
What is current I in the circuit as shown in figure?- a)1 A
- b)2.0 A
- c)1.2 A
- d)0.5 A
Correct answer is option 'B'. Can you explain this answer?
What is current I in the circuit as shown in figure?
a)
1 A
b)
2.0 A
c)
1.2 A
d)
0.5 A
|
|
Preeti Iyer answered |
Three 2Ω resistors are in series. Their total resistance =6Ω. Now it is in parallel with 2Ω resistor, so total resistance,
1/R=1/2+1/6=3+1/6=4/6=2/3
R=3/2
∴I=RV=3/(3/2)=3×2/3=2A
1/R=1/2+1/6=3+1/6=4/6=2/3
R=3/2
∴I=RV=3/(3/2)=3×2/3=2A
Manganin and constantan have a low temperature coefficient of resistivity which means that- a)their resistance values change very little with temperature
- b)their resistance values only change at low temperatures
- c)their resistance values change greatly with temperature
- d)their resistance values do not change with temperature
Correct answer is option 'A'. Can you explain this answer?
Manganin and constantan have a low temperature coefficient of resistivity which means that
a)
their resistance values change very little with temperature
b)
their resistance values only change at low temperatures
c)
their resistance values change greatly with temperature
d)
their resistance values do not change with temperature
|
|
Rajat Kapoor answered |
The semiconductors and insulating material are having negative temperature coefficient of resistance. Therefore, the resistance of semiconductors and insulators decrease with rise in temperature. Alloys, such as manganin, constantan etc. are having very low and positive temperature coefficient of resistance.
An electric bulb is rated 220 V and 100 W. Power consumed by it operated on 110 V is- a)90 W
- b)75 W
- c)25 W
- d)50 W
Correct answer is option 'C'. Can you explain this answer?
An electric bulb is rated 220 V and 100 W. Power consumed by it operated on 110 V is
a)
90 W
b)
75 W
c)
25 W
d)
50 W
|
|
Preeti Iyer answered |
P = V^2/R
If V = 220 V we have
100 W = 220^2/R
R = 220^2/100 Ω = 484 Ω. This is the resistance of the bulb.
When V = 110 V, power consumed = V^2/R = 110^2 /484 = 25 W.
The internal resistance of a battery cannot be measured with a conventional multimeter- a)since the resistance has a small value
- b)since it is not a measurable quantity
- c)since it requires a current to be observed
- d)since it is a fictitious quantity
Correct answer is option 'C'. Can you explain this answer?
The internal resistance of a battery cannot be measured with a conventional multimeter
a)
since the resistance has a small value
b)
since it is not a measurable quantity
c)
since it requires a current to be observed
d)
since it is a fictitious quantity
|
Manish Aggarwal answered |
The correct option is C
since it requires a current to be observed
It can be calculated from current and voltage data measured from a test circuit containing the battery and a load resistor
Flow of charges in direction of electrons is called
- a)current
- b)electronic current
- c)conventional current
- d)photonic current
Correct answer is option 'B'. Can you explain this answer?
Flow of charges in direction of electrons is called
a)
current
b)
electronic current
c)
conventional current
d)
photonic current
|
|
Anjali Iyer answered |
-
Current: This is a general term for the flow of electric charge. It can refer to any type of charge flow, not specifically electrons.
-
Electronic current: This specifically refers to the flow of electrons through a conductor.
-
Conventional current: This is the flow of positive charge and is considered to flow from the positive side to the negative side of a power source. Historically, this was defined before the discovery of electrons, so it is opposite to the direction of electron flow.
-
Photonic current: This is not a standard term in electrical engineering or physics. It might refer to currents related to photons in some contexts, but it is not related to the flow of electrons.
So, if you are referring to the flow of electrons specifically, electronic current is the accurate term.
A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/quantities constant along the length of the conductor is/are- a)Current and drift speed
- b)Current, electric field and drift velocity
- c)Speed only
- d)Current only.
Correct answer is option 'D'. Can you explain this answer?
A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/quantities constant along the length of the conductor is/are
a)
Current and drift speed
b)
Current, electric field and drift velocity
c)
Speed only
d)
Current only.
|
|
Rahul Bansal answered |
Steady current implies current is uniform across the cross-section.
Since current is constant, current per unit area and hence drift velocity are not constant.
J = nevd = σE
The above relation shows that nothing apart from the current is constant.
Two special characteristics of the element of an electric heater:- a)low resistivity and high melting point
- b)low resistivity and low melting point
- c)high resistivity and low melting point
- d)high resistivity and high melting point
Correct answer is option 'D'. Can you explain this answer?
Two special characteristics of the element of an electric heater:
a)
low resistivity and high melting point
b)
low resistivity and low melting point
c)
high resistivity and low melting point
d)
high resistivity and high melting point
|
Samiksha Narwade answered |
Electric heater is device to heat water.... So when it have high melting pt. it we sustain heat nd won't melt....nd resistance means to oppose heat... So it should have high resistivity to heat water without getting damage....HOPE THIS WILL HELP YOU....!
The equivalent emf of two cells (with ε1 > ε2) in series if we connect two negative electrodes of adjacent cells is- a)εequivalent =
- b)εequivalent =
- c)εequivalent = ε2 - ε1 (ε1 > ε2)
- d)εequivalent = ε1 - ε2 (ε1 > ε2)
Correct answer is option 'D'. Can you explain this answer?
The equivalent emf of two cells (with ε1 > ε2) in series if we connect two negative electrodes of adjacent cells is
a)
εequivalent =
b)
εequivalent =
c)
εequivalent = ε2 - ε1 (ε1 > ε2)
d)
εequivalent = ε1 - ε2 (ε1 > ε2)
|
Tannu Rathee answered |
D is the correct answer
Resistors can be wire bound or carbon resistors. Wire bound resistors are generally made of- a)Aluminium
- b)Carbon
- c)Copper
- d)Manganin
Correct answer is option 'D'. Can you explain this answer?
Resistors can be wire bound or carbon resistors. Wire bound resistors are generally made of
a)
Aluminium
b)
Carbon
c)
Copper
d)
Manganin
|
|
Anjana Sharma answered |
The wire material has a high resistivity, and is usually made of an alloy such as Nickel-chromium (Nichrome) or a copper-nickel-manganese alloy called Manganin. Common core materials include ceramic, plastic and glass. Wire wound resistors are the oldest type of resistors that are still manufactured today.
- a)0.04 V
- b)40.0 V
- c)0.4 V
- d)4.0 V
Correct answer is 'D'. Can you explain this answer?
|
Keerthana Iyer answered |
Given:
- e.m.f of first cell = 2V
- Balance point with first cell = 30cm
- Balance point with second cell = 60cm
To find:
- e.m.f of the second cell
Explanation:
To understand this problem, we need to understand the working principle of a potentiometer. A potentiometer is a device used to measure potential difference (or voltage) accurately. It consists of a long wire of uniform cross-section, a jockey, and a galvanometer.
When the jockey is moved along the wire, the galvanometer shows a deflection. At a certain point, the deflection becomes zero, indicating that the potential difference across that point is equal to the potential difference across the terminals of the cell being tested.
In this problem, the balance point with the first cell is at 30cm. This means that the potential difference across 30cm of the wire is equal to the e.m.f of the first cell, which is 2V.
Now, when the cell is replaced by another cell, the balance point shifts to 60cm. This means that the potential difference across 60cm of the wire is equal to the e.m.f of the second cell.
To find the e.m.f of the second cell, we can use the concept of proportionality. The potential difference across the wire is directly proportional to the length of the wire. So, we can set up the following proportion:
Potential difference across 30cm / Length of the wire = Potential difference across 60cm / Length of the wire
Since the length of the wire is the same on both sides of the equation, we can simplify the proportion to:
Potential difference across 30cm = Potential difference across 60cm
Substituting the given values:
2V = Potential difference across 60cm
Therefore, the e.m.f of the second cell is 2V.
Answer:
The e.m.f of the other cell is 4.0V (Option D).
- e.m.f of first cell = 2V
- Balance point with first cell = 30cm
- Balance point with second cell = 60cm
To find:
- e.m.f of the second cell
Explanation:
To understand this problem, we need to understand the working principle of a potentiometer. A potentiometer is a device used to measure potential difference (or voltage) accurately. It consists of a long wire of uniform cross-section, a jockey, and a galvanometer.
When the jockey is moved along the wire, the galvanometer shows a deflection. At a certain point, the deflection becomes zero, indicating that the potential difference across that point is equal to the potential difference across the terminals of the cell being tested.
In this problem, the balance point with the first cell is at 30cm. This means that the potential difference across 30cm of the wire is equal to the e.m.f of the first cell, which is 2V.
Now, when the cell is replaced by another cell, the balance point shifts to 60cm. This means that the potential difference across 60cm of the wire is equal to the e.m.f of the second cell.
To find the e.m.f of the second cell, we can use the concept of proportionality. The potential difference across the wire is directly proportional to the length of the wire. So, we can set up the following proportion:
Potential difference across 30cm / Length of the wire = Potential difference across 60cm / Length of the wire
Since the length of the wire is the same on both sides of the equation, we can simplify the proportion to:
Potential difference across 30cm = Potential difference across 60cm
Substituting the given values:
2V = Potential difference across 60cm
Therefore, the e.m.f of the second cell is 2V.
Answer:
The e.m.f of the other cell is 4.0V (Option D).
The dimension of the temperature coefficient of resistivity is- a)(temperature.ohm)-1
- b)same as temperature.ohm
- c)same as (temperature)-1
- d)same as (temperature)2
Correct answer is option 'C'. Can you explain this answer?
The dimension of the temperature coefficient of resistivity is
a)
(temperature.ohm)-1
b)
same as temperature.ohm
c)
same as (temperature)-1
d)
same as (temperature)2
|
|
Ameya Pillai answered |
Temperature Coefficient of Resistivity
The temperature coefficient of resistivity is defined as the change in the electrical resistance of a material per unit change in temperature. It is denoted by the symbol α and has units of inverse temperature (K^-1) or reciprocal temperature (1/T).
Effect of Temperature on Electrical Resistance
When the temperature of a conductor increases, its electrical resistance also increases. This is due to the fact that as the temperature increases, the atoms in the conductor vibrate more vigorously, which results in more collisions between the electrons and the atoms. This increase in collisions leads to an increase in the resistance of the conductor.
Formula for Temperature Coefficient of Resistivity
The temperature coefficient of resistivity is given by the formula:
α = (1/ρ) x (dρ/dT)
where ρ is the resistivity of the material and dρ/dT is the rate of change of the resistivity with temperature.
Dimension of Temperature Coefficient of Resistivity
The dimension of the temperature coefficient of resistivity is the same as that of reciprocal temperature or (temperature)^-1. This can be seen from the formula for the temperature coefficient of resistivity:
α = (1/ρ) x (dρ/dT)
where ρ has units of ohm-meters (Ω.m) and dρ/dT has units of ohm-meters per Kelvin (Ω.m/K). Thus, the units of α are K^-1 or 1/T.
Conclusion
In conclusion, the temperature coefficient of resistivity is a measure of how the electrical resistance of a material changes with temperature. It has units of inverse temperature or reciprocal temperature, and its dimension is the same as that of (temperature)^-1.
The temperature coefficient of resistivity is defined as the change in the electrical resistance of a material per unit change in temperature. It is denoted by the symbol α and has units of inverse temperature (K^-1) or reciprocal temperature (1/T).
Effect of Temperature on Electrical Resistance
When the temperature of a conductor increases, its electrical resistance also increases. This is due to the fact that as the temperature increases, the atoms in the conductor vibrate more vigorously, which results in more collisions between the electrons and the atoms. This increase in collisions leads to an increase in the resistance of the conductor.
Formula for Temperature Coefficient of Resistivity
The temperature coefficient of resistivity is given by the formula:
α = (1/ρ) x (dρ/dT)
where ρ is the resistivity of the material and dρ/dT is the rate of change of the resistivity with temperature.
Dimension of Temperature Coefficient of Resistivity
The dimension of the temperature coefficient of resistivity is the same as that of reciprocal temperature or (temperature)^-1. This can be seen from the formula for the temperature coefficient of resistivity:
α = (1/ρ) x (dρ/dT)
where ρ has units of ohm-meters (Ω.m) and dρ/dT has units of ohm-meters per Kelvin (Ω.m/K). Thus, the units of α are K^-1 or 1/T.
Conclusion
In conclusion, the temperature coefficient of resistivity is a measure of how the electrical resistance of a material changes with temperature. It has units of inverse temperature or reciprocal temperature, and its dimension is the same as that of (temperature)^-1.
Electromotive force is a- a)non contact force
- b)potential
- c)potential difference
- d)contact force
Correct answer is option 'C'. Can you explain this answer?
Electromotive force is a
a)
non contact force
b)
potential
c)
potential difference
d)
contact force
|
Shankar Shankar answered |
EMF
is
equal to
potential difference between plates when the battery is not connected to any external circuit.
Potential difference is due to the charge accumulation on the plates. So
EMF produces a
potential difference between the two terminals which drives the current
Unit of power is- a)newton
- b)joule
- c)watt
- d)newton sec
Correct answer is option 'C'. Can you explain this answer?
Unit of power is
a)
newton
b)
joule
c)
watt
d)
newton sec
|
Rahul Desai answered |
Power is rate of doing work.P=W/t.The unit of power is J/s which is also called watt.
Chapter doubts & questions for Current Electricity - Physics for ACT 2025 is part of ACT exam preparation. The chapters have been prepared according to the ACT exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for ACT 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.
Chapter doubts & questions of Current Electricity - Physics for ACT in English & Hindi are available as part of ACT exam.
Download more important topics, notes, lectures and mock test series for ACT Exam by signing up for free.
