Solution:
Key concept: Meter bridge: In case of meter bridge, the resistance wire AC is 100cm long. Varying the position of tapping point B, bridge is balanced. If in balanced position of bridge AB = l, BC = (100 - l) so that $\frac{\text{Q}}{\text{P}}=\frac{(100-\text{I})}{\text{I}}$. Also $\frac{\text{P}}{\text{Q}}=\frac{\text{R}}{\text{S}}>\text{S}=\frac{(100-\text{I})}{\text{I R}}$.
When there is no deflection in galvanometer there is no current across the galvanometer, then points B and D are at same potential. That point at which galvanometer shows no deflection is called null point, then potential at B and neutral point D are same. When the jockey contacts a point on the meter wire to the right of D, the potential drop across AD is more than potential drop across AB, which brings the potential of point D less than that of B, hence current flows from B to D in the galvanometer wire.
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If only 2% of the main current is to be passed through a galvanometer of resistance G, then the resistance of shunt will be
|
(a) |
(b) |
(c) 50 G |
(d) 49 G |
An arbitrary shaped closed coil is made of a wire of length L and a current I ampere is flowing in it. If the plane of the coil is perpendicular to magnetic field 
, the force on the coil is
|
(a) Zero |
(b) IBL |
(c) 2IBL |
(d) |
Which statement is correct
|
(a) N-type germanium is negatively charged and P-type germanium is positively charged |
|
(b) Both N-type and P-type germanium are neutral |
|
(c) N-type germanium is positively charged and P-type germanium is negatively charged |
|
(d) Both N-type and P-type germanium are negatively charged |
Two parallel wires of length 9 m each are separated by a distance 0.15 m. If they carry equal currents in the same direction and exerts a total force of 30 × 10–7 N on each other, then the value of current must be
|
(a) 2.5 amp |
(b) 3.5 amp |
(c) 1.5 amp |
(d) 0.5 amp |
The capacity of an air condenser is 2.0 mF. If a medium is placed between its plates. The capacity becomes 12 mF. The dielectric constant of the medium will be
|
(a) 5 |
(b) 4 |
(c) 3 |
(d) 6 |
The electric field due to an electric dipole at a distance r from its centre in axial position is E. If the dipole is rotated through an angle of 90° about its perpendicular axis, the electric field at the same point will be
|
(a) E |
(b) E/4 |
(c) E/2 |
(d) 2E |
