Current Electricity
Q. Two resistors of 4Ω and 6Ω are connected in parallel. What is the equivalent resistance?
A.
2.4Ω
B.
3.6Ω
C.
4Ω
D.
5Ω
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Solution
Using the formula for parallel resistors, 1/R_eq = 1/R1 + 1/R2 = 1/4 + 1/6 = 5/12, R_eq = 12/5 = 2.4Ω.
Correct Answer: B — 3.6Ω
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Q. Using Kirchhoff's Current Law, if three currents enter a junction as 2A, 3A, and I, what is the value of I if the total current leaving the junction is 5A?
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Solution
According to KCL, I = total entering - total leaving = (2A + 3A) - 5A = 0A.
Correct Answer: B — 1A
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Q. Using Kirchhoff's Current Law, if three currents enter a junction as 3A, 2A, and I, what is the value of I if the total current leaving the junction is 5A?
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Solution
According to KCL, I = Total entering - Total leaving = (3A + 2A) - 5A = 0A.
Correct Answer: A — 4A
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Q. Using Kirchhoff's Voltage Law, if a loop in a circuit has a 12V battery and two resistors of 4Ω and 6Ω, what is the voltage drop across the 4Ω resistor?
A.
4.8V
B.
8V
C.
6V
D.
3.2V
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Solution
Using voltage division, V_R1 = V_total * (R1 / (R1 + R2)) = 12V * (4Ω / (4Ω + 6Ω)) = 12V * (4/10) = 4.8V.
Correct Answer: B — 8V
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Q. Using Kirchhoff's Voltage Law, if a loop in a circuit has a 12V battery and two resistors of 4Ω and 6Ω, what is the voltage across the 4Ω resistor?
A.
4.8V
B.
8V
C.
6V
D.
3.2V
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Solution
Using voltage division, V_R1 = (R1 / (R1 + R2)) * V_total = (4Ω / (4Ω + 6Ω)) * 12V = 4.8V.
Correct Answer: B — 8V
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Q. Using Kirchhoff's voltage law, if a loop in a circuit has a 9V battery and two resistors (2Ω and 3Ω) with voltage drops of 4V and 5V respectively, is the loop correctly analyzed?
A.
Yes
B.
No
C.
Only if the battery is 12V
D.
Only if the resistors are in series
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Solution
According to Kirchhoff's voltage law, the sum of the voltage drops must equal the source voltage. Here, 4V + 5V = 9V, which is correct.
Correct Answer: B — No
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Q. What does Ohm's Law state?
A.
Voltage is directly proportional to current
B.
Current is directly proportional to resistance
C.
Resistance is directly proportional to voltage
D.
Voltage is inversely proportional to current
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Solution
Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points, which can be expressed as V = IR.
Correct Answer: A — Voltage is directly proportional to current
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Q. What happens to the balancing length if the emf of the cell is increased while keeping the potentiometer wire constant?
A.
Balancing length increases
B.
Balancing length decreases
C.
No change in balancing length
D.
Balancing length becomes zero
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Solution
Increasing the emf of the cell increases the balancing length, as it requires a longer length to balance the higher voltage.
Correct Answer: A — Balancing length increases
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Q. What happens to the current in a circuit if the resistance is increased while the voltage remains constant?
A.
It increases
B.
It decreases
C.
It remains the same
D.
It becomes zero
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Solution
According to Ohm's Law, if resistance increases while voltage remains constant, the current decreases.
Correct Answer: B — It decreases
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Q. What happens to the current in a circuit if the voltage is tripled and the resistance remains constant?
A.
It triples
B.
It doubles
C.
It halves
D.
It remains the same
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Solution
According to Ohm's Law, if voltage (V) is tripled and resistance (R) remains constant, the current (I) will also triple: I = V / R.
Correct Answer: A — It triples
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Q. What happens to the current in the galvanometer when the Wheatstone bridge is balanced?
A.
Increases
B.
Decreases
C.
Becomes zero
D.
Fluctuates
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Solution
When the Wheatstone bridge is balanced, the current in the galvanometer becomes zero.
Correct Answer: C — Becomes zero
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Q. What happens to the current through the galvanometer when the bridge is balanced?
A.
It increases.
B.
It decreases.
C.
It becomes zero.
D.
It becomes maximum.
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Solution
When the bridge is balanced, the current through the galvanometer becomes zero.
Correct Answer: C — It becomes zero.
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Q. What happens to the current through the galvanometer when the Wheatstone bridge is perfectly balanced?
A.
It flows in one direction.
B.
It flows in both directions.
C.
It is zero.
D.
It is maximum.
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Solution
When the Wheatstone bridge is perfectly balanced, the current through the galvanometer is zero.
Correct Answer: C — It is zero.
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Q. What happens to the current through the galvanometer when the Wheatstone bridge is unbalanced?
A.
It becomes zero
B.
It increases
C.
It decreases
D.
It becomes infinite
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Solution
When the Wheatstone bridge is unbalanced, there is a non-zero potential difference across the galvanometer, causing current to flow through it.
Correct Answer: B — It increases
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Q. What happens to the current through the galvanometer when the Wheatstone bridge is balanced?
A.
It increases
B.
It decreases
C.
It becomes zero
D.
It becomes infinite
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Solution
When the Wheatstone bridge is balanced, the potential difference across the galvanometer is zero, resulting in zero current through it.
Correct Answer: C — It becomes zero
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Q. What happens to the galvanometer reading in a Wheatstone bridge when it is balanced?
A.
It shows maximum current
B.
It shows minimum current
C.
It shows zero current
D.
It shows fluctuating current
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Solution
When the Wheatstone bridge is balanced, the potential difference across the galvanometer is zero, resulting in zero current.
Correct Answer: C — It shows zero current
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Q. What happens to the null point in a potentiometer if the resistance of the wire is increased?
A.
Null point moves towards the battery
B.
Null point moves away from the battery
C.
Null point remains unchanged
D.
Null point becomes unstable
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Solution
Increasing the resistance of the wire decreases the current, which causes the null point to move away from the battery.
Correct Answer: B — Null point moves away from the battery
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Q. What happens to the potential difference across a segment of a potentiometer wire if the resistance of the wire is increased?
A.
It increases.
B.
It decreases.
C.
It remains the same.
D.
It becomes zero.
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Solution
Increasing the resistance of the wire decreases the current, which in turn decreases the potential difference across any segment of the wire.
Correct Answer: C — It remains the same.
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Q. What happens to the potential difference across a segment of a potentiometer wire if the length of that segment is halved?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It becomes zero
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Solution
If the length of the segment is halved, the potential difference across that segment also halves, assuming the potential gradient remains constant.
Correct Answer: B — It halves
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Q. What happens to the reading of a potentiometer if the resistance of the wire increases?
A.
Reading increases
B.
Reading decreases
C.
Reading remains the same
D.
Reading becomes zero
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Solution
The reading of a potentiometer is independent of the resistance of the wire as long as the potential difference remains constant.
Correct Answer: C — Reading remains the same
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Q. What happens to the reading of a potentiometer if the temperature of the wire increases?
A.
It increases.
B.
It decreases.
C.
It remains constant.
D.
It becomes zero.
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Solution
As temperature increases, the resistance of the wire typically increases, which can affect the potential gradient and thus the reading.
Correct Answer: B — It decreases.
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Q. What happens to the reading of a potentiometer if the wire is heated and its resistance increases?
A.
Reading increases
B.
Reading decreases
C.
Reading remains the same
D.
Reading becomes zero
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Solution
If the wire is heated and its resistance increases, the reading of the potentiometer decreases because the potential gradient will be affected.
Correct Answer: B — Reading decreases
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Q. What happens to the reading on a potentiometer when the resistance of the galvanometer is increased?
A.
Reading increases
B.
Reading decreases
C.
Reading remains the same
D.
Reading becomes zero
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Solution
Increasing the resistance of the galvanometer reduces the current through it, which can lead to a decrease in the reading on the potentiometer.
Correct Answer: B — Reading decreases
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Q. What happens to the resistance of a conductor if its temperature increases?
A.
It decreases.
B.
It increases.
C.
It remains the same.
D.
It becomes zero.
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Solution
For most conductors, resistance increases with an increase in temperature due to increased atomic vibrations.
Correct Answer: B — It increases.
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Q. What happens to the resistance of a wire if its diameter is halved while keeping the length constant?
A.
It doubles
B.
It halves
C.
It quadruples
D.
It remains the same
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Solution
Resistance R is inversely proportional to the area; halving the diameter quarters the area, thus quadrupling the resistance.
Correct Answer: C — It quadruples
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Q. What happens to the resistivity of a superconductor as it approaches absolute zero?
A.
Increases
B.
Decreases
C.
Becomes infinite
D.
Becomes zero
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Solution
The resistivity of a superconductor approaches zero as it reaches absolute zero.
Correct Answer: D — Becomes zero
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Q. What happens to the resistivity of a superconductor as it transitions to the superconducting state?
A.
Increases
B.
Decreases
C.
Becomes zero
D.
Remains constant
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Solution
In the superconducting state, the resistivity of a superconductor becomes zero.
Correct Answer: C — Becomes zero
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Q. What happens to the sensitivity of a Wheatstone bridge if the resistances are made equal?
A.
Sensitivity increases
B.
Sensitivity decreases
C.
Sensitivity remains the same
D.
Sensitivity becomes infinite
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Solution
If the resistances are made equal, the sensitivity of the Wheatstone bridge becomes infinite, as even a small change will cause a large deflection.
Correct Answer: D — Sensitivity becomes infinite
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Q. What happens to the total current in a parallel circuit if one of the branches is disconnected?
A.
Total current increases
B.
Total current decreases
C.
Total current remains the same
D.
Total current becomes zero
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Solution
If one branch is disconnected, the total current decreases because there is less path for the current to flow.
Correct Answer: B — Total current decreases
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Q. What happens to the total resistance in a circuit when more resistors are added in series?
A.
It decreases
B.
It increases
C.
It remains the same
D.
It becomes zero
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Solution
In a series circuit, the total resistance increases as more resistors are added.
Correct Answer: B — It increases
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