An alternating e.m.f. of angular frequency ω is applied across an inductance. The instantaneous power developed across it has an angular frequency
(a) ω/4
(b) ω/2
(c) ω
(d) 2 ω
(a) ω/4
(b) ω/2
(c) ω
(d) 2 ω
(d) 2 ω
A capacitor of capacity C has reactance X. If capacitance and frequency become double then reactance will be
(a) 4X
(b) X/2
(c) X/4
(d) 2X
A 40 mF capacitor is connected to a 200 V, 50 Hz ac supply. The r.m.s value of the current in the circuit is, nearly
(a) 1.7 A
(b) 2.05 A
(c) 2.5 A
(d) 25.1 A
In electric arc furnace Cu or Iron is melted due to variation of
(a) current
(b) magnetic field
(c) voltage
(d) electric field
In series R-L-C circuit, quality factor can be improved by
(a) decreasing L
(b) increasing C
(c) decreasing R
(d) decreasing R & L
In an A.C. circuit, Irms and I₀ are related as
(a) Irms = p I₀
(b) Irms = 2 I₀
(c) Irms = I₀/p
(d) Irms =I₀ / 2
Show that in the free oscillations of an LC circuit, the sum of energies stored in the capacitor and the inductor is constant in time.
State which of the two a capacitor or an inductor, tends to become SHORT when the frequency of the applied alternating voltage has a high value.
When a body charges by conduction, its mass
(A) Remains same
(B) Increases
(C)Decreases
(D)Increase or decrease
Magnetic field lines form continuous closed loops
a) magnet is always a dipole
b) magnet is always a monopole
c) magnetic material is permeable
d) none of the above
If 100 J of work has to be done in moving an electric charge of 4 C from a place, where potential is -10 volt to another place where potential is V volt,find the value of V.
(a) 5 V
(b) 10 V
(c) 25 V
(d) 15 V
Two sources of light are said to be coherent, when they give light waves of same
(a) amplitude and phase.
(b) wavelength and constant phase difference.
(c) intensity and wavelength.
(d) phase and speed.
A small signal voltage V(t) = V₀ sin(ωt) is applied across an ideal capacitor C
(a) Current I(t) is in phase with voltage V(t).
(b) Current I(t) leads voltage V(t) by 180°.
(c) Current I(t), lags voltage V(t) by 90°.
(d) Over a full cycle the capacitor C does not consume any energy from the voltage source
The magnetic flux linked with a coil is given by the equation Ø = 2t² + 2t + 4 weber. The magnitude of induced emf at time t=2s will be
(a) 16 V
(b) 10V
(c) 12V
(d) 8V
Which of the following is not a property of electric field lines?
(A) Field lines are closed and continuous curves without any breaks.
(B) Two field lines cannot cross each other.
(C) Field lines start at positive charges and end at negative charges.
(D) They do not form closed loops.