Magnetism and Matter — Physics STD 12 Science — Question

The particles which can be added to the nucleus of an atom without changing its chemical properties are called

(a) Electrons

(b) Protons

(c) Neutrons

(d) None of the above

A plano-convex lens of refractive index 1.5 and radius of curvature 30 cm is silvered at the curved surface. Now this lens has been used to form the image of an object. At what distance from this lens an object be placed in order to have a real image of the size of the object

(a) 20 cm

(b) 30 cm

(c) 60 cm

(d) 80 cm

Eight dipoles of charges of magnitude e are placed inside a cube. The total electric flux coming out of the cube will be

(a)

(b)

(c)

(d) Zero

If the two ends of a p-n junction are joined by a wire:

1. There will not be a steady current in the circuit.
2. There will be a steady current from the n-side to the p-side.
3. There 'will a steady current from the p-side. to the n-side.
4. There may or may not be a current depending upon the resistance of the connecting wire.

Resistance of capacitor for high frequency is:

A semiconductor device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be a/ an?

Threshold frequency is the frequency :

What is the potential energy of the equal positive point charges of 1μC each held 1 m apart in air

(a) 9

(b) 9

(c) 2 eV/m

(d) Zero

A magnet of magnetic moment M oscillating freely in earth's horizontal magnetic field makes n oscillations per minute. If the magnetic moment is quadrupled and the earth's field is doubled, the number of oscillations made per minute would be

(a)

(b)

(c) 2

(d)