Explanation:
According to the right-hand thumb rule, if we curl the fingers of our right hand in the direction of the current flowing, then the stretching of the thumb will show the direction of the magnetic field developed due to it and vice versa.
Let north-south is along x axis and east-west is along y axis. Circular wire is in xz plane. Then point A will lie on positive y axis and B on negative y axis. On looking from point B, current is flowing in anticlockwise direction so the magnetic field will point from right to left. Hence, the magnetic field due to the loop will be towards west at both A and B.
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In the circuit of a triode valve, there is no change in the plate current, when the plate potential is increased from 200 volt to 220 volt and the grid potential is decreased from – 0.5 volt to –1.3 volt. The amplification factor of this valve is
|
(a) 15 |
(b) 20 |
(c) 25 |
(d) 35 |
If an observer is moving with respect to a stationary electron, then he observes
|
(a) Only magnetic field |
(b) Only electric field |
(c) Both (a) and (b) |
(d) None of the above |
A mass m = 20 g has a charge q = 30 mC. It moves with a velocity of 20 m/s and enters a region of electric field of 80 N/C in the same direction as the velocity of the mass. The velocity of the mass after 3 seconds in this region is
|
(a) 80 m/s |
(b) 56 m/s |
(c) 44 m/s |
(d) 40 m/s |
Seven resistances are connected as shown in the figure. The equivalent resistance between A and B is
|
(a) 3 W |
(b) 4 W |
(c) 4.5 W |
(d) 5 W |
A long copper tube of inner radius R carries a current i. The magnetic field B inside the tube is
|
(a) |
(b) |
(c) |
(d) Zero |
