Electric Charges and Fields — Physics STD 12 Science — Question

A steady current flows in a metallic conductor of non-uniform cross-section. Which of the following quantities is constant along the conductor?

Dynamo core is laminated because

(a) Magnetic field increases

(b) Magnetic saturation level in core increases

(c) Residual magnetism in core decreases

(d) Loss of energy in core due to eddy currents decreases

Sinusoidal carrier voltage of frequency 1.5 MHz and amplitude 50 V is amplitude modulated by sinusoidal voltage of frequency 10 kHz producing 50% modulation. The lower and upper side-band frequencies in kHz are

(a) 1490, 1510

(b) 1510, 1490

(c)

(d)

Maxwell’s equations describe the fundamental laws of

(a) Electricity only

(b) Magnetism only

(c) Mechanics only

(d) Both (a) and (b)

In a cathode ray tube, what is the effect on the beam of particles if a hotter filament is used?

In the above question, the power lost in the cable during transmission is

(a) 12.5 kW

(b) 6.25 kW

(c) 25 kW

(d) 3.15 kW

A free neutron decays to a proton but a free proton does not decay to a neutron. This is because:

1. Neutron is a composite particle made of a proton and an electron whereas proton is a fundamental particle.
2. Neutron is an uncharged particle whereas proton is a charged particle.
3. Neutron has large rest mass than the proton.
4. Weak forces can operate in a neutron but not in a proton.

In an insulator, the energy gap between conduction band and valence band is about:

The equivalent capacitance of the combination shown in figure is: