Electric Charges and Fields — Physics STD 12 Science — Question

The direction of magnetic lines of forces close to a straight conductor carrying current will be

(a) Along the length of the conductor

(a) Along the length of the conductor

(c) Circular in a plane perpendicular to the conductor

(d) Helical

A plane electromagnetic wave of frequency 20 MHz travels through a space along x direction. If the electric field vector at a certain point in space is 6V m^-1, what is the magnetic field vector at that point?

A long thin hollow metallic cylinder of radius 'R' has a current i ampere. The magnetic induction 'B'-away from the axis at a distance r from the axis varies as shown in

(a)

(b)

(c)

(d)

A parallel-plate capacitor has plates of unequal area. The larger plate is connected to the positive terminal of the battery and the smaller plate to its negative terminal. Let Q₊ and Q_- be the charges appearing on the positive and negative plates respectively:

1. Q₊ > Q_-
2. Q₊ = Q_-
3. Q₊ < Q_-
4. The information is not sufficient to decide the relation between Q₊ and Q_-.

The resistance of a germanium junction diode whose V - I  is shown in figure is  

(a) 5 kW

(b) 0.2 kW

(c) 2.3 kW

(d)

Figure, shows some of the electric field lines corresponding to an electric field. The figure suggests that,

The electric potential at the surface of an atomic nucleus (Z = 50) of radius 9.0 ×   cm is

(a) 80 volts

(b) 8  volts

(c) 9 volts

(d) 9  volts

A parallel plate capacitor with air as medium between the plates has a capacitance of 10 μF. The area of capacitor is divided into two equal halves and filled with two media as shown in the figure having dielectric constant  and . The capacitance of the system will now be

(a) 10 μF

(b) 20 μF

(c) 30 μF

(d) 40 μF

In an insulator, the forbidden energy gap between the valence band and conduction band is of the order of: