Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

Which of the following represents the binding energy of a nucleus:

Cathode rays are produced when the pressure is of the order of

(a) 2 cm of Hg

(b) 0.1 cm of Hg

(c) 0.01 mm of Hg

(d) 1 μm of Hg

Three α - particles and one β - particle decaying takes place in series from an isotope . Finally the isotope obtained will be

(a)

(b)

(c)

(d)

An oxide coated filament is useful in vacuum tubes because essentially

(a) It has high melting point

(b) It can withstand high temperatures

(c) It has good machanical strength

(d) It can emit electrons at relatively lower temperatures

An external resistance R is connected to a battery of e.m.f. V and internal resistance r. The joule heat produced in resistor R is maximum when R is equal to

(a)  r

(b)

(c) 2r

(d) Infinitely large

A hot electric iron has a resistance of 80 Ω and is used on a 200 V source. The electrical energy spent, if it is used for two hours, will be

(a) 8000 Wh

(b) 2000 Wh

(c) 1000 Wh

(d) 800 Wh

For protecting a sensitive equipment from the external magnetic field, it should be

(a) Placed inside an aluminium cane

(b) Placed inside an iron cane

(c) Wrapped with insulation around it when passing current through it

(d) Surrounded with fine copper sheet

Force between the two parallel wires carrying currents has been used to define:

Electric potential is given by T, hen electric force acting on 2C  point charge placed on origin will be

(a) 2N

(b) 6N

(c) 8N

(d) 20 N