- AThe direction of current is always positive
- BThe direction of current is always negative
- CThe direction of current changes constantly
- DThe direction of current is either positive or negative
Explanation:
Electric charge in alternating current (AC) changes direction periodically. The voltage in AC circuits also periodically reverses because the current changes direction.
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X-rays of
have frequency
|
(a) 3 |
(b) 3 |
(c) |
(d) |
At a place the value of horizontal component of the earth's magnetic field H is 3
. A metallic rod AB of length 2 m placed in east-west direction, having the end A towards east, falls vertically downward with a constant velocity of 50 m/s. Which end of the rod becomes positively charged and what is the value of induced potential difference between the two ends
|
(a) End A, 3 |
(b) End A, 3 mV |
|
(c) End B, 3 |
(d) End B, 3 mV |
A battery of emf 10 V and internal resistance 3Ω is connected to a resistor as shown in the figure. If the current in the circuit is 0.5 A. then the resistance of the resistor will be
|
(a) 19 W |
(b) 17 W |
(c) 10 W |
(d) 12 W |
The antenna current of an AM transmitter is 8 A when only carrier is sent but increases to 8.96 A when the carrier is sinusoidally modulated. The percentage modulation is
|
(a) 50% |
(b) 60% |
(c) 65% |
(d) 71% |
A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, the new value of the magnetic field is
|
(a) B |
(b) 2 B |
(c) 4 B |
(d) B/2 |