In a purely resistive a.c. circuit, the current
(a) is in phase with the e.m.f.
(b) leads the e.m.f. by a difference of π radians phase
(c) leads the e.m.f. by a phase difference of π/2 radians
(d) lags behind the e.m.f. by a phase difference of π/4 radians
(a) is in phase with the e.m.f.
(b) leads the e.m.f. by a difference of π radians phase
(c) leads the e.m.f. by a phase difference of π/2 radians
(d) lags behind the e.m.f. by a phase difference of π/4 radians
(a) is in phase with the e.m.f.
In highly inductive load circuit, it is more dangerous when
(a) we close the switch
(b) open the switch
(c) increasing the resistance
(d) decreasing the resistance
In a series LCR circuit, obtain the conditions under which
(i) the impedance of the circuit is minimum, and
(ii) wattless current flows in the circuit.
A lamp is connected in series with a capacitor. Predict your observation for dc and ac connections. What happens in each if the capacitance of the capacitor is reduced ?
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
A 200 mH (pure) inductor and a 5 µF (pure) capacitor are connected one by one, across a sinusoidal ac voltage source of V = [70.7sin (1000t)] voltage. Obtain the expression for the current in each case.
In electric arc furnace Cu or Iron is melted due to variation of
(a) current
(b) magnetic field
(c) voltage
(d) electric field
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.
The speed of light in air is 3 × \(10^8\) m/s. If the refractive index of glass is 1.5, find the time taken by light to travel a distance 50 cm in glass.
(a) 2.5 × \(10^{-9}\) sec.
(b) 0.5 × \(10^{-9}\) sec.
(c) 0.16 × \(10^{-9}\) sec.
(d) 3 × \(10^{-9}\) sec.
In a Wheatstone bridge, three resistors P,Q, R are connected in three arms in order and 4th arm of resistance, s, is formed by two resistors s1 and s2 connected in parallel. The condition for bridge to be balanced is, P/Q
The ratio of magnetic length to geometric length of a magnet is
a) 0.084
b) 8.4
c) 80.4
d) 0.84
Graph represents q verses V for two capacitors having same plate separation but different plate area . Which is the correct option
In Young’s double slit experiment the distance between the slit and the screen is doubled and the separation between the slit is reduced to half. The fringe width:
(a) is doubled
(b) become four time
(c) is halved
(d) remain unchanged
A parrot comes and sits on a bare high-power line. It will
A. experience a mild shock
B. experiences a strong shock
C. get killed instantaneously
D. not be affected at all
In Young’s double slit experiment, the central point on the screen is:
(a) bright
(b) dark
(c) first bright and later dark
(d) first dark and later bright