37
In a uniform magnetic field of 0.049 T, a magnetic needle performs 20 oscillations in 5 seconds. The moment of inertia is \(9.8 × 10^{-6} \, \text{kg m}^2\). The magnetic moment is \(x × 10^{-5} \, \text{Am}^2\). The value of x is:
Correct Answer:D
Explanation:
Using \(T = 2π\sqrt{\frac{I}{MB}}\), solve for M (magnetic moment).
38
In an ideal transformer with turns ratio \(\frac{N_p}{N_s} = \frac{1}{2}\), the ratio \(V_s : V_p\) is:
Correct Answer:B
Explanation:
Transformer voltage ratio equals turns ratio: \(\frac{V_s}{V_p} = \frac{N_s}{N_p}\).
39
In a vernier calipers, (N+1) vernier divisions coincide with N main scale divisions. If 1 MSD = 0.1 mm, the vernier constant (in cm) is:
Correct Answer:B
Explanation:
Vernier constant = \(\frac{1 \text{MSD}}{N+1} = \frac{0.1 \text{mm}}{N+1}\), converted to cm.
40
A horizontal force of 10 N is applied to block A (2 kg) and block B (3 kg) on a frictionless surface. The force exerted by A on B is:
Correct Answer:C
Explanation:
Acceleration of the system is \(a = \frac{F}{m_A + m_B}\). Force on B is \(m_B × a\).
41
If \(x = 5\sin(πt + \frac{π}{3})\) m represents SHM, the amplitude and time period are:
Correct Answer:B
Explanation:
Amplitude = 5 m. Time period \(T = \frac{2π}{ω} = 2 \, \text{s}\) (since ω = π rad/s).
42
The terminal voltage of a battery (emf = 10V, internal resistance = 1Ω) connected to a 4Ω resistor is:
Correct Answer:C
Explanation:
Terminal voltage \(V = EMF - Ir\), where \(I = \frac{EMF}{R + r}\).