Q. A coil of wire has 100 turns and is placed in a magnetic field of strength 0.5 T. If the area of the coil is 0.1 m² and the magnetic field is perpendicular to the coil, what is the magnetic flux through the coil? (2022)
A.
5 Wb
B.
0.5 Wb
C.
10 Wb
D.
0.05 Wb
Solution
Magnetic flux (Φ) = B × A × cos(θ). Here, B = 0.5 T, A = 0.1 m², and θ = 0° (cos(0) = 1). Thus, Φ = 0.5 T × 0.1 m² × 1 = 0.05 Wb.
Q. A coil of wire has 100 turns and is placed in a magnetic field of strength 0.5 T. If the area of the coil is 0.1 m², what is the maximum magnetic flux through the coil? (2022)
A.
5 Wb
B.
0.5 Wb
C.
10 Wb
D.
1 Wb
Solution
Magnetic flux (Φ) = B × A × N = 0.5 T × 0.1 m² × 100 = 5 Wb.
Q. A coil with 100 turns has a magnetic flux of 0.02 Wb passing through it. If the flux changes to 0.01 Wb in 2 seconds, what is the induced EMF? (2022)
Q. A loop of wire is moved into a magnetic field at a constant speed. What happens to the induced current as the loop enters the magnetic field? (2023)
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
Solution
As the loop enters the magnetic field, the change in magnetic flux increases, leading to an increase in the induced current.
Q. A loop of wire is placed in a uniform magnetic field. If the magnetic field is increased uniformly, what happens to the induced current in the loop?
A.
It increases
B.
It decreases
C.
It remains constant
D.
It becomes zero
Solution
According to Faraday's law, an increase in magnetic field through the loop induces a current in the loop, which increases as the rate of change of magnetic flux increases.
Q. A loop of wire is rotated in a uniform magnetic field. What is the effect on the induced current? (2019)
A.
It remains constant
B.
It reverses direction
C.
It increases
D.
It decreases
Solution
As the loop rotates, the angle between the magnetic field and the normal to the loop changes, which causes the direction of the induced current to reverse periodically.
Q. A solenoid has a length of 1 m and a cross-sectional area of 0.01 m². If the magnetic field inside the solenoid is 0.2 T, what is the magnetic flux through one turn of the solenoid?
A.
0.002 Wb
B.
0.01 Wb
C.
0.02 Wb
D.
0.1 Wb
Solution
Magnetic flux (Φ) = B * A = 0.2 T * 0.01 m² = 0.002 Wb. For one turn, the flux is 0.002 Wb.
Q. A transformer has 200 turns in the primary coil and 50 turns in the secondary coil. If the primary voltage is 240 V, what is the secondary voltage? (2023)
A.
60 V
B.
120 V
C.
240 V
D.
480 V
Solution
Using the transformer equation Vp/Vs = Np/Ns, we find Vs = Vp × (Ns/Np) = 240 V × (50/200) = 60 V.
Q. According to Faraday's law of electromagnetic induction, the induced EMF in a circuit is proportional to the rate of change of which of the following? (2020)
A.
Magnetic field strength
B.
Magnetic flux
C.
Electric field strength
D.
Current
Solution
Faraday's law states that the induced EMF in a circuit is directly proportional to the rate of change of magnetic flux through the circuit.
Q. According to Faraday's law of electromagnetic induction, the induced EMF in a circuit is directly proportional to the rate of change of which of the following? (2020)
A.
Magnetic field strength
B.
Magnetic flux
C.
Electric current
D.
Resistance
Solution
Faraday's law states that the induced EMF is proportional to the rate of change of magnetic flux through the circuit.
Q. If the area of a coil is doubled while keeping the magnetic field constant, what happens to the magnetic flux through the coil? (2023)
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
Solution
Magnetic flux (Φ) is given by the product of magnetic field (B) and area (A). If the area is doubled and the magnetic field remains constant, the magnetic flux also doubles.
Q. If the area of a loop in a magnetic field is doubled while keeping the magnetic field strength constant, what happens to the magnetic flux through the loop?
A.
It doubles
B.
It halves
C.
It remains the same
D.
It quadruples
Solution
Magnetic flux (Φ) is given by Φ = B * A. If the area (A) is doubled and the magnetic field (B) remains constant, the magnetic flux also doubles.
Q. In an AC generator, the induced EMF is maximum when the coil is positioned at what angle to the magnetic field?
A.
0 degrees
B.
45 degrees
C.
90 degrees
D.
180 degrees
Solution
In an AC generator, the induced EMF is maximum when the coil is positioned at 90 degrees to the magnetic field, as this is when the rate of change of magnetic flux is greatest.
