Physics
Q. What happens to the magnetic field when the distance from a long straight conductor is doubled? (2023)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
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Solution
The magnetic field around a long straight conductor decreases with distance. Specifically, it is inversely proportional to the distance from the conductor.
Correct Answer: B — It halves
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Q. What is the capacitance of a capacitor that stores 10 µC of charge at a potential difference of 5 V?
A.
2 µF
B.
5 µF
C.
10 µF
D.
20 µF
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Solution
C = Q/V = 10 × 10^-6 C / 5 V = 2 × 10^-6 F = 2 µF.
Correct Answer: A — 2 µF
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Q. What is the capacitive reactance of a capacitor of 10μF at a frequency of 60 Hz? (2016)
A.
265.26Ω
B.
159.15Ω
C.
100Ω
D.
50Ω
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Solution
Capacitive reactance Xc = 1 / (2πfC) = 1 / (2π * 60 * 10e-6) = 265.26Ω.
Correct Answer: A — 265.26Ω
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Q. What is the capacitive reactance of a capacitor with a capacitance of 10μF at a frequency of 50Hz? (2020)
A.
318.31 ohms
B.
159.15 ohms
C.
31.83 ohms
D.
15.92 ohms
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Solution
Xc = 1 / (2πfC) = 1 / (2π × 50 × 10 × 10^-6) = 318.31 ohms.
Correct Answer: A — 318.31 ohms
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Q. What is the change in internal energy of a system if 200 J of heat is added and 50 J of work is done by the system?
A.
150 J
B.
250 J
C.
200 J
D.
100 J
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Solution
Using the first law of thermodynamics, ΔU = Q - W = 200 J - 50 J = 150 J.
Correct Answer: A — 150 J
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Q. What is the change in internal energy of a system if 300 J of heat is added and 100 J of work is done by the system? (2021)
A.
200 J
B.
300 J
C.
400 J
D.
500 J
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Solution
Using the first law of thermodynamics: ΔU = Q - W = 300 J - 100 J = 200 J.
Correct Answer: A — 200 J
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Q. What is the current through a 10Ω resistor connected to a 20V battery? (2020)
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Solution
Using Ohm's law, I = V/R = 20V / 10Ω = 2A.
Correct Answer: B — 2A
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Q. What is the current through a 12Ω resistor connected to a 24V battery? (2023)
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Solution
Using Ohm's law, I = V/R = 24V / 12Ω = 2A.
Correct Answer: B — 2A
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Q. What is the current through a 12Ω resistor when a voltage of 48V is applied? (2023)
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Solution
Using Ohm's law, I = V/R = 48V / 12Ω = 4A.
Correct Answer: B — 6A
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Q. What is the current through a 15Ω resistor connected to a 45V source? (2021)
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Solution
Using Ohm's law, I = V/R = 45V / 15Ω = 3A.
Correct Answer: A — 3A
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Q. What is the direction of the magnetic field around a straight conductor carrying current? (2023)
A.
From north to south
B.
Clockwise
C.
Counterclockwise
D.
Radially outward
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Solution
The direction of the magnetic field around a straight conductor carrying current is counterclockwise when viewed from the positive end of the conductor.
Correct Answer: C — Counterclockwise
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Q. What is the effect of a dielectric material on the capacitance of a capacitor? (2023)
A.
It decreases the capacitance
B.
It increases the capacitance
C.
It has no effect
D.
It makes the capacitor discharge
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Solution
Inserting a dielectric material increases the capacitance of a capacitor by reducing the electric field within it.
Correct Answer: B — It increases the capacitance
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Q. What is the effect of increasing the capacitance in a capacitive AC circuit on the current? (2022)
A.
Increases current
B.
Decreases current
C.
No effect
D.
Current becomes zero
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Solution
Increasing capacitance increases the current in a capacitive AC circuit, as current I = V/Xc.
Correct Answer: A — Increases current
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Q. What is the effect of increasing the current in a coil on the magnetic field produced? (2022)
A.
Increases the magnetic field
B.
Decreases the magnetic field
C.
No effect
D.
Reverses the magnetic field
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Solution
Increasing the current in a coil increases the magnetic field produced by the coil.
Correct Answer: A — Increases the magnetic field
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Q. What is the effect of increasing the current in a solenoid on its magnetic field strength? (2021)
A.
Increases
B.
Decreases
C.
No effect
D.
Reverses direction
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Solution
Increasing the current in a solenoid increases its magnetic field strength, as the magnetic field is directly proportional to the current.
Correct Answer: A — Increases
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Q. What is the effect of increasing the frequency on the capacitive reactance in an AC circuit? (2022)
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
Capacitive reactance Xc = 1/(2πfC), so increasing frequency decreases Xc.
Correct Answer: B — Decreases
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Q. What is the effect of increasing the frequency on the impedance of a capacitor? (2023)
A.
Increases
B.
Decreases
C.
Remains constant
D.
Becomes infinite
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Solution
The impedance of a capacitor decreases with increasing frequency.
Correct Answer: B — Decreases
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Q. What is the effect of increasing the frequency on the total impedance of an RLC circuit? (2020)
A.
It always increases
B.
It always decreases
C.
It can increase or decrease
D.
It remains constant
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Solution
The total impedance can increase or decrease depending on the relationship between R, XL, and XC as frequency changes.
Correct Answer: C — It can increase or decrease
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Q. What is the effect on the fringe separation in a double-slit experiment if the distance between the slits and the screen is increased? (2021)
A.
Fringe separation decreases
B.
Fringe separation increases
C.
Fringe separation remains the same
D.
Fringe separation becomes zero
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Solution
Fringe separation is directly proportional to the distance from the slits to the screen. Increasing this distance increases the fringe separation.
Correct Answer: B — Fringe separation increases
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Q. What is the effect on the total resistance in a series circuit if one resistor is removed? (2023)
A.
Increases
B.
Decreases
C.
Remains the same
D.
Becomes zero
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Solution
Removing a resistor from a series circuit decreases the total resistance since the sum of the remaining resistances is less.
Correct Answer: B — Decreases
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Q. What is the efficiency of a Carnot engine operating between 300 K and 600 K? (2022)
A.
0.5
B.
0.33
C.
0.25
D.
0.67
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Solution
Efficiency = 1 - (T_c/T_h) = 1 - (300/600) = 0.5.
Correct Answer: A — 0.5
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Q. What is the efficiency of a Carnot engine operating between 500 K and 300 K? (2022)
A.
0.4
B.
0.5
C.
0.6
D.
0.7
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Solution
Efficiency = 1 - (T2/T1) = 1 - (300/500) = 0.4 or 40%.
Correct Answer: C — 0.6
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Q. What is the efficiency of a Carnot engine operating between a hot reservoir at 600 K and a cold reservoir at 300 K?
A.
0.5
B.
0.33
C.
0.25
D.
0.75
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Solution
Efficiency (η) = 1 - (T_c/T_h) = 1 - (300/600) = 0.5 or 50%.
Correct Answer: B — 0.33
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Q. What is the efficiency of a Carnot engine operating between temperatures of 500 K and 300 K?
A.
0.4
B.
0.5
C.
0.6
D.
0.7
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Solution
Efficiency (η) = 1 - (T2/T1) = 1 - (300/500) = 0.4 or 40%.
Correct Answer: C — 0.6
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Q. What is the electric field due to a point charge at a distance 'r' from it? (2021)
A.
k * q / r^2
B.
k * q / r
C.
k * q * r
D.
k * q * r^2
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Solution
The electric field (E) due to a point charge (q) at a distance (r) is given by E = k * q / r^2, where k is Coulomb's constant.
Correct Answer: A — k * q / r^2
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Q. What is the electric field due to a point charge of +3 µC at a distance of 0.3 m?
A.
30 N/C
B.
90 N/C
C.
300 N/C
D.
900 N/C
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Solution
E = k * |q| / r^2 = (9 × 10^9) * (3 × 10^-6) / (0.3)^2 = 90 N/C.
Correct Answer: B — 90 N/C
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Q. What is the electric potential at a point 0.4 m away from a charge of +5 µC?
A.
45 V
B.
50 V
C.
55 V
D.
60 V
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Solution
V = k * q / r = (9 × 10^9) * (5 × 10^-6) / 0.4 = 112.5 V.
Correct Answer: B — 50 V
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Q. What is the electric potential at a point due to a charge Q at a distance r? (2021)
A.
kQ/r
B.
kQr
C.
kQ/r^2
D.
0
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Solution
The electric potential (V) at a distance r from a point charge Q is given by V = kQ/r.
Correct Answer: A — kQ/r
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Q. What is the equivalent resistance of two 4Ω resistors in parallel? (2019)
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Solution
Using the formula 1/R_eq = 1/R1 + 1/R2, we get 1/R_eq = 1/4 + 1/4 = 1/2, thus R_eq = 2Ω.
Correct Answer: A — 2Ω
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Q. What is the equivalent resistance of two resistors of 4Ω and 12Ω in parallel? (2022)
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Solution
Using the formula 1/R_eq = 1/R1 + 1/R2, we get 1/R_eq = 1/4 + 1/12 = 1/3, so R_eq = 3Ω.
Correct Answer: A — 3Ω
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