Current Electricity
Q. In a circuit with two resistors in series, if R1 = 4Ω and R2 = 6Ω, what is the total resistance?
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Solution
The total resistance in series is R_total = R1 + R2 = 4Ω + 6Ω = 10Ω.
Correct Answer: D — 10Ω
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Q. In a circuit with two resistors in series, if the total resistance is 12 ohms and one resistor is 4 ohms, what is the value of the other resistor?
A.
8 ohms
B.
4 ohms
C.
12 ohms
D.
16 ohms
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Solution
Using the formula for resistors in series, R_total = R1 + R2, we have 12 = 4 + R2, thus R2 = 12 - 4 = 8 ohms.
Correct Answer: A — 8 ohms
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Q. In a circuit with two resistors in series, if the total voltage across the circuit is 12V and the resistors have values of 4Ω and 6Ω, what is the voltage across the 4Ω resistor?
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Solution
Using the voltage divider rule, V1 = (R1 / (R1 + R2)) * Vtotal = (4 / (4 + 6)) * 12 = 4.8V.
Correct Answer: B — 6V
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Q. In a circuit with two resistors in series, if the total voltage across the circuit is 12V and the resistors are 4Ω and 6Ω, what is the voltage across the 4Ω resistor?
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Solution
Using the voltage divider rule, V1 = (R1 / (R1 + R2)) * Vtotal = (4 / (4 + 6)) * 12 = 4.8V.
Correct Answer: A — 4V
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Q. In a circuit, if the voltage across a resistor is 12V and the current through it is 3A, what is the resistance?
A.
4 ohms
B.
3 ohms
C.
2 ohms
D.
1 ohm
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Solution
Using Ohm's law, R = V/I = 12V / 3A = 4 ohms.
Correct Answer: A — 4 ohms
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Q. In a circuit, if the voltage across a resistor is doubled, what happens to the current through it?
A.
Doubles
B.
Halves
C.
Remains the same
D.
Quadruples
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Solution
According to Ohm's law, if voltage is doubled and resistance remains constant, current also doubles.
Correct Answer: A — Doubles
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Q. In a circuit, if the voltage is halved and the resistance remains constant, what happens to the current?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
According to Ohm's law, if voltage is halved while resistance remains constant, current also halves.
Correct Answer: B — It halves
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Q. In a circuit, if the voltage is increased from 5V to 15V while the resistance remains constant at 5 ohms, what is the change in current?
A.
Increases by 1 A
B.
Increases by 2 A
C.
Increases by 3 A
D.
Increases by 4 A
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Solution
Initial current I1 = 5V / 5Ω = 1 A; Final current I2 = 15V / 5Ω = 3 A; Change in current = I2 - I1 = 3 A - 1 A = 2 A.
Correct Answer: C — Increases by 3 A
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Q. In a circuit, if the voltage is increased while keeping the resistance constant, what happens to the current?
A.
It decreases
B.
It increases
C.
It remains constant
D.
It becomes zero
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Solution
According to Ohm's Law, if voltage increases and resistance remains constant, the current will increase.
Correct Answer: B — It increases
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Q. In a circuit, if the voltage is increased while the resistance remains constant, what happens to the current?
A.
It decreases
B.
It increases
C.
It remains the same
D.
It becomes zero
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Solution
According to Ohm's Law, if the voltage (V) increases and resistance (R) remains constant, the current (I) increases.
Correct Answer: B — It increases
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Q. In a closed loop circuit, if the sum of the currents entering a junction is 10A and the sum of the currents leaving the junction is 6A, what is the current flowing through the junction?
A.
4A
B.
6A
C.
10A
D.
16A
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Solution
According to Kirchhoff's current law, the current flowing into the junction must equal the current flowing out. Therefore, 10A - 6A = 4A is the current flowing through the junction.
Correct Answer: A — 4A
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Q. In a closed loop circuit, if the sum of the voltage rises is 10V and the sum of the voltage drops is 6V, what is the net voltage in the loop according to Kirchhoff's Voltage Law?
A.
4V
B.
6V
C.
10V
D.
16V
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Solution
According to Kirchhoff's Voltage Law, the net voltage in the loop is the sum of rises minus the sum of drops: 10V - 6V = 4V.
Correct Answer: A — 4V
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Q. In a closed loop circuit, if the sum of the voltage rises is 20V and the sum of the voltage drops is 15V, what is the net voltage in the loop according to Kirchhoff's Voltage Law?
A.
5V
B.
15V
C.
20V
D.
35V
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Solution
According to Kirchhoff's Voltage Law, the net voltage in the loop is the sum of voltage rises minus the sum of voltage drops: 20V - 15V = 5V.
Correct Answer: A — 5V
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Q. In a material with a resistivity of 2 x 10^-8 Ω·m, what is the resistance of a 10 m long wire with a cross-sectional area of 1 mm²?
A.
0.02 Ω
B.
0.2 Ω
C.
2 Ω
D.
20 Ω
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Solution
Resistance R = ρ(L/A) = 2 x 10^-8 * (10 / (1 x 10^-6)) = 0.2 Ω.
Correct Answer: B — 0.2 Ω
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Q. In a material with a resistivity of 2 x 10^-8 Ω·m, what is the resistance of a 3 m long wire with a cross-sectional area of 1 mm²?
A.
0.006 Ω
B.
0.018 Ω
C.
0.024 Ω
D.
0.036 Ω
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Solution
Resistance R = ρ(L/A) = 2 x 10^-8 * (3 / (1 x 10^-6)) = 0.024 Ω.
Correct Answer: C — 0.024 Ω
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Q. In a parallel circuit with three resistors of 2Ω, 3Ω, and 6Ω, what is the equivalent resistance?
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Solution
The equivalent resistance for resistors in parallel is given by 1/R_eq = 1/R1 + 1/R2 + 1/R3. Thus, 1/R_eq = 1/2 + 1/3 + 1/6 = 1. Therefore, R_eq = 1Ω.
Correct Answer: B — 2Ω
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Q. In a parallel circuit with three resistors of 6 ohms, 12 ohms, and 18 ohms, what is the equivalent resistance?
A.
3 ohms
B.
4 ohms
C.
2 ohms
D.
1 ohm
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Solution
Using the formula for resistors in parallel, 1/R_eq = 1/R1 + 1/R2 + 1/R3, we find R_eq = 1 / (1/6 + 1/12 + 1/18) = 3 ohms.
Correct Answer: A — 3 ohms
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Q. In a parallel circuit with three resistors of values 2Ω, 3Ω, and 6Ω, what is the equivalent resistance?
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Solution
1/R_eq = 1/R1 + 1/R2 + 1/R3 = 1/2 + 1/3 + 1/6 = 1. Therefore, R_eq = 3Ω.
Correct Answer: C — 3Ω
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Q. In a parallel circuit with three resistors of values 6 ohms, 3 ohms, and 2 ohms, what is the equivalent resistance?
A.
1.5 ohms
B.
2 ohms
C.
2.5 ohms
D.
3 ohms
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Solution
The formula for equivalent resistance in parallel is 1/R_eq = 1/R1 + 1/R2 + 1/R3. Thus, 1/R_eq = 1/6 + 1/3 + 1/2 = 1/6 + 2/6 + 3/6 = 6/6 = 1, so R_eq = 1 ohm.
Correct Answer: C — 2.5 ohms
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Q. In a parallel circuit with three resistors R1 = 2Ω, R2 = 3Ω, and R3 = 6Ω, what is the equivalent resistance?
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Solution
The equivalent resistance in parallel is given by 1/R_total = 1/R1 + 1/R2 + 1/R3. Thus, 1/R_total = 1/2 + 1/3 + 1/6 = 1Ω.
Correct Answer: A — 1Ω
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Q. In a parallel circuit with two resistors of 4 ohms and 6 ohms, what is the equivalent resistance?
A.
2.4 ohms
B.
10 ohms
C.
24 ohms
D.
12 ohms
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Solution
For parallel resistors, 1/R_eq = 1/R1 + 1/R2. Thus, 1/R_eq = 1/4 + 1/6 = 5/12, so R_eq = 12/5 = 2.4 ohms.
Correct Answer: A — 2.4 ohms
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Q. In a parallel circuit with two resistors of 4 ohms and 6 ohms, what is the total current if the voltage across the circuit is 12V?
A.
2 A
B.
3 A
C.
4 A
D.
5 A
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Solution
First, find the equivalent resistance: 1/R_eq = 1/4 + 1/6 => R_eq = 2.4 ohms. Then, I = V/R_eq = 12V / 2.4Ω = 5 A.
Correct Answer: B — 3 A
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Q. In a parallel circuit with two resistors of 4 ohms and 6 ohms, what is the total current if the voltage across the circuit is 12 V?
A.
2 A
B.
3 A
C.
4 A
D.
5 A
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Solution
First, find the equivalent resistance: 1/R_eq = 1/4 + 1/6 => R_eq = 2.4 ohms. Then, I = V/R_eq = 12 V / 2.4 ohms = 5 A.
Correct Answer: B — 3 A
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Q. In a parallel circuit with two resistors of 4Ω and 6Ω, what is the total current if the voltage across the circuit is 12V?
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Solution
First, find the equivalent resistance: 1/R_eq = 1/4 + 1/6 => R_eq = 2.4Ω. Then, I = V/R_eq = 12V / 2.4Ω = 5A.
Correct Answer: B — 3A
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Q. In a parallel circuit with two resistors of 6 ohms and 3 ohms, what is the equivalent resistance?
A.
2 ohms
B.
4 ohms
C.
1.5 ohms
D.
9 ohms
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Solution
Using the formula for resistors in parallel, 1/R_eq = 1/R1 + 1/R2, we have 1/R_eq = 1/6 + 1/3 = 1/6 + 2/6 = 3/6. Therefore, R_eq = 6/3 = 2 ohms.
Correct Answer: B — 4 ohms
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Q. In a parallel circuit with two resistors R1 = 6Ω and R2 = 3Ω, what is the equivalent resistance?
A.
2Ω
B.
4Ω
C.
1.5Ω
D.
9Ω
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Solution
1/R_eq = 1/R1 + 1/R2 = 1/6 + 1/3 = 1/6 + 2/6 = 3/6, thus R_eq = 2Ω.
Correct Answer: A — 2Ω
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Q. In a parallel circuit, if one resistor fails, what happens to the total current?
A.
It increases.
B.
It decreases.
C.
It remains the same.
D.
It becomes zero.
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Solution
In a parallel circuit, if one resistor fails, the total current decreases because the total resistance increases.
Correct Answer: B — It decreases.
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Q. In a parallel circuit, if one resistor is removed, what happens to the total resistance?
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes infinite
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Solution
In a parallel circuit, removing a resistor decreases the total resistance.
Correct Answer: B — Decreases
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Q. In a potentiometer circuit, if the balancing length is 50 cm for a cell of emf 1.5V, what is the potential gradient if the total length of the wire is 100 cm?
A.
3 V/m
B.
1.5 V/m
C.
0.75 V/m
D.
2 V/m
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Solution
The potential gradient is V/L = 1.5V/0.5m = 3 V/m, but since the total length is 1m, the gradient is 1.5 V/m.
Correct Answer: C — 0.75 V/m
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Q. In a potentiometer circuit, if the length of the wire is doubled while keeping the potential difference constant, what happens to the potential gradient?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It becomes zero
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Solution
The potential gradient is defined as the potential difference per unit length. If the length is doubled while keeping the potential difference constant, the potential gradient halves.
Correct Answer: B — It halves
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