Current Electricity
Q. A wire has a resistance of 10 ohms at 20°C. If the temperature coefficient of resistivity is 0.004/°C, what will be its resistance at 100°C?
A.
10.4 ohms
B.
12 ohms
C.
14 ohms
D.
16 ohms
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Solution
R = R0(1 + α(T - T0)) = 10(1 + 0.004(100 - 20)) = 10(1 + 0.32) = 10.4 ohms.
Correct Answer: B — 12 ohms
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Q. A wire has a resistance of 10 Ω at 20°C. If the temperature coefficient of resistivity is 0.004/°C, what will be the resistance at 100°C?
A.
10 Ω
B.
12 Ω
C.
14 Ω
D.
16 Ω
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Solution
R = R0(1 + α(T - T0)) = 10(1 + 0.004(100 - 20)) = 10(1 + 0.32) = 10(1.32) = 13.2 Ω.
Correct Answer: C — 14 Ω
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Q. A wire has a resistance of 10 Ω at 20°C. If the temperature coefficient of resistivity is 0.004/°C, what will be its resistance at 100°C?
A.
10 Ω
B.
12 Ω
C.
14 Ω
D.
16 Ω
Show solution
Solution
R = R0(1 + α(T - T0)) = 10(1 + 0.004(100 - 20)) = 10(1 + 0.32) = 10(1.32) = 13.2 Ω.
Correct Answer: C — 14 Ω
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Q. A wire has a resistance of 12 Ω and is made of a material with a resistivity of 3 x 10^-6 Ω·m. If the length of the wire is 4 m, what is its cross-sectional area?
A.
0.5 mm²
B.
1 mm²
C.
2 mm²
D.
3 mm²
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Solution
A = ρ * (L / R) = 3 x 10^-6 * (4 / 12) = 1 mm².
Correct Answer: B — 1 mm²
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Q. A wire has a resistance of 12 Ω. If it is stretched to double its length, what will be the new resistance assuming uniform cross-section?
A.
24 Ω
B.
48 Ω
C.
12 Ω
D.
6 Ω
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Solution
Resistance R is proportional to length; if length doubles, resistance also doubles to 24 Ω.
Correct Answer: A — 24 Ω
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Q. A wire has a resistance of 5 Ω at 20°C. If the temperature coefficient of resistivity is 0.004/°C, what will be its resistance at 100°C?
A.
5.4 Ω
B.
6.4 Ω
C.
7.4 Ω
D.
8.4 Ω
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Solution
R = R0(1 + α(T - T0)) = 5(1 + 0.004(100 - 20)) = 6.4 Ω.
Correct Answer: B — 6.4 Ω
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Q. A wire made of material A has a resistivity of 1.5 x 10^-8 Ω·m, while material B has a resistivity of 3.0 x 10^-8 Ω·m. If both wires have the same dimensions, which wire will have a higher resistance?
A.
Wire A
B.
Wire B
C.
Both have the same resistance
D.
Cannot be determined
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Solution
Resistance is directly proportional to resistivity; hence, wire B with higher resistivity will have higher resistance.
Correct Answer: B — Wire B
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Q. A wire made of material A has twice the length and half the cross-sectional area of a wire made of material B. If the resistivity of A is ρ, what is the resistance of wire A in terms of the resistance of wire B?
A.
2R
B.
4R
C.
R/2
D.
R/4
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Solution
Resistance R = ρ(L/A). For wire A, R_A = ρ(2L/(A/2)) = 4ρ(L/A) = 4R_B.
Correct Answer: B — 4R
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Q. A wire of length 10 m and cross-sectional area 2 mm² has a resistance of 3 Ω. What is the resistivity of the material?
A.
1.5 x 10^-6 Ω·m
B.
3 x 10^-6 Ω·m
C.
6 x 10^-6 Ω·m
D.
1.5 x 10^-5 Ω·m
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Solution
Resistivity ρ = R * (A / L) = 3 * (2 x 10^-6 / 10) = 1.5 x 10^-6 Ω·m.
Correct Answer: A — 1.5 x 10^-6 Ω·m
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Q. According to Kirchhoff's Current Law, if three currents enter a junction as 2A, 3A, and 4A, what is the total current leaving the junction?
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Solution
According to Kirchhoff's Current Law, the total current entering a junction equals the total current leaving it. Total entering = 2A + 3A + 4A = 9A.
Correct Answer: D — 9A
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Q. According to Kirchhoff's Current Law, if three currents enter a junction as 2A, 3A, and 4A, what is the current leaving the junction?
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Solution
According to Kirchhoff's Current Law, the sum of currents entering a junction equals the sum of currents leaving. Therefore, I_out = 2A + 3A + 4A = 9A.
Correct Answer: D — 9A
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Q. According to Kirchhoff's Current Law, if three currents enter a junction as 2A, 3A, and 1A, what is the total current leaving the junction?
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Solution
According to Kirchhoff's Current Law, total current entering = total current leaving. 2A + 3A + 1A = 6A.
Correct Answer: B — 5A
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Q. According to Kirchhoff's Current Law, if three currents entering a junction are 2A, 3A, and 5A, what is the total current leaving the junction?
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Solution
According to Kirchhoff's Current Law, the total current entering a junction equals the total current leaving it. Therefore, total current leaving = 2A + 3A + 5A = 10A.
Correct Answer: A — 10A
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Q. According to Kirchhoff's Voltage Law, the sum of the potential differences around any closed loop in a circuit is equal to what?
A.
Zero
B.
The total current
C.
The total resistance
D.
The total power
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Solution
Kirchhoff's Voltage Law states that the sum of the electromotive forces and potential differences in any closed loop is zero.
Correct Answer: A — Zero
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Q. According to Kirchhoff's Voltage Law, the sum of the potential differences around any closed loop in a circuit must equal what?
A.
Zero
B.
The total current
C.
The total resistance
D.
The total power
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Solution
Kirchhoff's Voltage Law states that the sum of the electrical potential differences (voltage) around any closed circuit is zero.
Correct Answer: A — Zero
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Q. If a 10 ohm resistor is connected to a 20V battery, what is the energy consumed in 5 seconds?
A.
20 J
B.
40 J
C.
10 J
D.
50 J
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Solution
Power P = V^2 / R = 20^2 / 10 = 40 W. Energy = Power * time = 40 W * 5 s = 200 J.
Correct Answer: B — 40 J
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Q. If a 10 ohm resistor is connected to a 30V battery, what is the energy consumed in 5 seconds?
A.
15 J
B.
30 J
C.
75 J
D.
150 J
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Solution
Power P = V^2 / R = (30V)^2 / 10 ohms = 90 W. Energy = Power * Time = 90 W * 5 s = 450 J.
Correct Answer: C — 75 J
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Q. If a 10Ω resistor is connected to a 20V battery, what is the power dissipated by the resistor?
A.
20W
B.
40W
C.
100W
D.
200W
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Solution
Power (P) can be calculated using P = V^2/R. Here, P = 20V^2 / 10Ω = 400 / 10 = 40W.
Correct Answer: B — 40W
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Q. If a 10Ω resistor is connected to a 20V source, what is the energy consumed in 5 seconds?
A.
20J
B.
40J
C.
50J
D.
100J
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Solution
Power P = V^2 / R = 20V^2 / 10Ω = 40W. Energy = Power * time = 40W * 5s = 200J.
Correct Answer: B — 40J
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Q. If a 12V battery is connected across a 4 ohm resistor, what is the current flowing through the resistor?
A.
2 A
B.
3 A
C.
4 A
D.
6 A
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Solution
Using Ohm's law, I = V/R = 12V / 4Ω = 3 A.
Correct Answer: A — 2 A
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Q. If a 12V battery is connected across a 4 ohm resistor, what is the power dissipated in the resistor?
A.
12 W
B.
24 W
C.
36 W
D.
48 W
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Solution
Power (P) can be calculated using P = V^2 / R = 12V^2 / 4Ω = 144 / 4 = 36 W.
Correct Answer: B — 24 W
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Q. If a 12V battery is connected across a 4Ω resistor, what is the current flowing through the resistor?
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Solution
Using Ohm's law, I = V/R = 12V / 4Ω = 3A.
Correct Answer: B — 2A
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Q. If a 12V battery is connected to a 4 ohm resistor, what is the power dissipated by the resistor?
A.
12 W
B.
24 W
C.
36 W
D.
48 W
Show solution
Solution
Power (P) can be calculated using P = V^2 / R = 12V^2 / 4Ω = 36 W.
Correct Answer: B — 24 W
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Q. If a 5 ohm resistor and a 10 ohm resistor are connected in series, what is the voltage across the 10 ohm resistor when a current of 2 A flows through the circuit?
A.
10 V
B.
20 V
C.
5 V
D.
15 V
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Solution
Voltage across the 10 ohm resistor, V = I * R = 2 A * 10 Ω = 20 V.
Correct Answer: B — 20 V
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Q. If a 5 ohm resistor is connected to a 10V battery, what is the energy consumed in 2 seconds?
A.
10 J
B.
20 J
C.
5 J
D.
15 J
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Solution
Power P = V^2 / R = 10^2 / 5 = 20 W. Energy = Power * time = 20 W * 2 s = 40 J.
Correct Answer: B — 20 J
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Q. If a 5 ohm resistor is connected to a 10V battery, what is the energy consumed in 2 minutes?
A.
60 J
B.
120 J
C.
240 J
D.
30 J
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Solution
Power P = V^2/R = 10^2 / 5 = 20 W. Energy = Power * time = 20 W * 120 s = 2400 J.
Correct Answer: B — 120 J
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Q. If a 5Ω resistor is connected in parallel with a 10Ω resistor, what is the equivalent resistance?
A.
3.33Ω
B.
5Ω
C.
7.5Ω
D.
15Ω
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Solution
R_eq = 1/(1/5 + 1/10) = 3.33Ω.
Correct Answer: A — 3.33Ω
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Q. If a 60W bulb operates at 120V, what is the resistance of the bulb?
A.
240 ohms
B.
120 ohms
C.
60 ohms
D.
30 ohms
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Solution
Using P = V^2 / R, R = V^2 / P = (120V)^2 / 60W = 240 ohms.
Correct Answer: B — 120 ohms
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Q. If a 60W light bulb operates at 120V, what is the resistance of the bulb?
A.
240 ohms
B.
120 ohms
C.
60 ohms
D.
30 ohms
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Solution
Power (P) = V^2 / R, so R = V^2 / P = (120V)^2 / 60W = 240 ohms.
Correct Answer: B — 120 ohms
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Q. If a 6V battery is connected to a circuit with a total resistance of 3 ohms, what is the current flowing through the circuit?
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Solution
Using Ohm's law, I = V/R = 6V / 3 ohms = 2A.
Correct Answer: B — 2A
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