In a circuit, the current lags behind the voltage by a phase difference of π/2, the circuit will contain which of the following?
Only R
Only C
R and C
Only L
D.
Only L
When a circuit contains inductance only, then the current lags behind the voltage by the phase difference of π/2 or 90°. While in a purely capacitive circuit, the current leads the voltage by a phase angle of π/2 or 90°. In a purely resistive circuit current is in phase with the applied voltage.
N identical cells, each of emf E, are connected in parallel. The emf of the combination is
NE
E
N2E
E/N
A 30 µF capacitor is charged by a constant current of 30 mA. If the capacitor is initially uncharged, how long does it take for the potential difference to reach 400 V?
0.2 s
0.4 s
0.6 s
0.8 s
The intensity of sound gets reduced by 10% on passing through a slab. The reduction in intensity on passing through two consecutive slabs would be
20 %
19 %
5 %
50 %
Four independent waves are expressed as
(i) and (iii)
(i) and (iv)
(ii) and (iv)
not possible at all
Two coherent monochromatic light beams of intensities I and 4 I superimpose. The maximum and minimum possible intensities in the resulting beam are respectively
5I and I
5I and 3I
3I and I
9I and I
Ordinary light incident on a glass slab at the polarising angle suffers a deviation of 22°. The value of the angle of refraction in glass in this case is
56°
68°
34°
22°
A radioisotope has a half-life of 5 yr. The fraction of the atoms of this material that would decay in 15 yr will be
1
2/3
7/8
5/8