Atoms — Physics STD 12 Science — Question

The effective resistance between the points  A and  B in the figure is

(a) 5Ω

(b) 2 Ω

(c) 3 Ω

(d) 4 Ω

If a current of 3.0 amperes flowing in the primary coil is reduced to zero in 0.001 second, then the induced e.m.f. in the secondary coil is 15000 volts. The mutual inductance between the two coils is

(a) 0.5 henry

(b) 5 henry

(c) 1.5 henry

(d) 10 henry

When the P end of P-N junction is connected to the negative terminal of the battery and the N end to the positive terminal of the battery, then the P-N junction behaves like          

(a) A conductor

(b) An insulator

(c) A super-conductor

(d) A semi-conductor

A current I flows along the length of an infinitely long, straight and thin-walled pipe. Then

(a) The magnetic field at all points inside the pipe is the same but not zero

(b) The magnetic field at any point inside the pipe is zero

(c) The magnetic field is zero only on the axis of the pipe

(d) The magnetic field is different at different points inside the pipe

Three capacitances of capacity 10 μF, 5 μF  and 5 μF  are connected in parallel. The total capacity will be

(a) 10 μF

(b) 5 μF

(c) 20 μF

(d) None of the above

Choose the correct option:

Scale used in moving coil galvanometer is:

When germanium is doped with phosphorus, the doped material has

(a) Excess positive charge	(b) Excess negative charge
(c) More negative current carriers	(d) More positive current carriers

If a spark is produced on removing the load from an AC circuit then the element connected in the circuit is.

When a metal is illuminated with light wave, then the minimum energy required to take an electron just out of the surface of the metal is called :