Electric Charges and Fields — Physics STD 12 Science — Question

The ratio of magnetic fields due to a small bar magnet in the end on position to the broad side on position is

If   is 6563 Å, then wave length of second line for Balmer series will be

(a)

(b)

(c)

(d) None of the above

For a cell of e.m.f. 2V, a balance is obtained for 50 cm of the potentiometer wire. If the cell is shunted by a  2Ω resistor and the balance is obtained across 40 cm of the wire, then the internal resistance of the cell is

(a) 0.25 Ω

(b) 0.50 Ω

(c) 0.80 Ω

(d) 1.00 Ω

In the nuclear reaction , the values of A and Z are

(a) A = 234, Z = 94

(b) A = 234, Z = 90

(c) A = 238, Z = 94

(d) A = 238, Z = 90

Relation between critical angles of water and glass is

(a) Cw > Cg

(b) Cw < Cg

(c) Cw = Cg

(d) Cw = Cg = 0

The potential gradient at which the dielectric of a condenser just gets punctured is called:

Energy released in the fission of a single   nucleus is 200 MeV. The fission rate of a  fuelled reactor operating at a power level of 5W is

(a) 1.56

(b) 1.56

(c) 1.56

(d) 1.56

A battery of e.m.f. E and internal resistance r is connected to a variable resistor R as shown here. Which one of the following is true

(a) Potential difference across the terminals of the battery is maximum when R = r

(b) Power delivered to the resistor is maximum when R = r

(c) Current in the circuit is maximum when R = r

(d) Current in the circuit is maximum when R >> r

If a current is passed in a spring, it

(a) Gets compressed

(b) Gets expanded

(c) Oscillates

(d) Remains unchanged

The circuit shown in following figure contains two diode D₁ and D₂ each with a forward resistance of 50 ohms and with infinite backward resistance. If the battery voltage is 6 V, the current through the 100 ohm resistance (in amperes) is

(a) Zero

(b) 0.02

(c) 0.03

(d) 0.036