Q. A circular loop is placed in a uniform magnetic field. If the loop is rotated about its diameter, what happens to the induced EMF?
A.It increases
B.It decreases
C.It remains constant
D.It becomes zero
Solution
When the loop is rotated about its diameter, the angle between the magnetic field and the normal to the loop changes, but the magnetic flux remains constant. Therefore, the induced EMF becomes zero as there is no change in magnetic flux.
Q. A circular loop of radius r is placed in a uniform magnetic field B. If the magnetic field is perpendicular to the plane of the loop, what is the magnetic flux through the loop?
A.0
B.πr²B
C.2πrB
D.B/r
Solution
The magnetic flux Φ through a surface is given by Φ = B * A, where A is the area. For a circular loop, A = πr², so Φ = B * πr².
Q. A coil of wire is placed in a magnetic field. If the magnetic field strength is increased, what happens to the induced EMF in the coil?
A.It increases
B.It decreases
C.It remains the same
D.It becomes zero
Solution
According to Faraday's law of electromagnetic induction, the induced EMF in a coil is directly proportional to the rate of change of magnetic flux. Increasing the magnetic field strength increases the magnetic flux, thus increasing the induced EMF.
Q. A loop of wire is moved into a magnetic field at a constant speed. What is the effect on the induced current as the loop enters the field?
A.It increases
B.It decreases
C.It remains constant
D.It becomes zero
Solution
As the loop enters the magnetic field, the area of the loop within the field increases, leading to an increase in magnetic flux and thus an increase in the induced current according to Faraday's law.
Q. A loop of wire is placed in a uniform magnetic field. If the angle between the field and the normal to the loop is 60 degrees, what is the effective magnetic flux?
A.0.5 B A
B.0.866 B A
C.0.866 B A²
D.B A
Solution
Effective magnetic flux (Φ) = B * A * cos(θ) = B * A * cos(60°) = 0.5 B A.
Q. A solenoid with a length of 1 m and a cross-sectional area of 0.01 m² carries a current of 5 A. If the magnetic field inside the solenoid is uniform, what is the magnetic field strength?
A.0.1 T
B.0.2 T
C.0.5 T
D.1 T
Solution
The magnetic field inside a solenoid is given by B = μ₀ * (N/L) * I. Assuming N/L = 1 for simplicity, B = μ₀ * I = 4π × 10^-7 T*m/A * 5 A = 0.5 T.
Q. A transformer operates on the principle of electromagnetic induction. If the primary coil has 100 turns and the secondary coil has 50 turns, what is the relationship between the primary and secondary voltages?
A.V_primary = 2 * V_secondary
B.V_primary = 0.5 * V_secondary
C.V_primary = V_secondary
D.V_primary = 4 * V_secondary
Solution
The voltage ratio in a transformer is given by the turns ratio. Therefore, V_primary/V_secondary = N_primary/N_secondary = 100/50 = 2, which means V_primary = 2 * V_secondary.
Q. A transformer operates on the principle of electromagnetic induction. What is the primary function of a transformer?
A.To increase voltage
B.To decrease voltage
C.To convert AC to DC
D.To store energy
Solution
A transformer is designed to increase or decrease the voltage in an AC circuit through electromagnetic induction, depending on the turns ratio of the primary and secondary coils.
Q. If a magnetic field is applied perpendicular to a loop of wire, what is the effect on the induced EMF?
A.It is maximum
B.It is minimum
C.It is zero
D.It fluctuates
Solution
When a magnetic field is applied perpendicular to a loop of wire, the magnetic flux through the loop is maximized, resulting in maximum induced EMF according to Faraday's law.
