Introduction to Physics — Physics STD 12 Science — Question

In a meter bridge, the balancing length from the left end (standard resistance of one ohm is in the right gap) is found to be 20 cm. The value of the unknown resistance is

(a) 0.8 Ω

(b) 0.5 Ω

(c) 0.4 Ω

(d) 0.25 Ω

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.

The radius of the convex surface of plano-convex lens is 20 cm and the refractive index of the material of the lens is 1.5. The focal length of the lens is

(a) 30 cm

(b) 50 cm

(c) 20 cm

(d) 40 cm

Temperature coefficient of resistance of semiconductor is:

The amount of heat produced in a resistor when a current is passed through it can be found using

(a) Faraday’s Law

(b) Kirchhoff’s Law

(c) Laplace’s Law

(d) Joule’s Law

A transistor has three impurity regions. All the three regions have different doping levels. In order of increasing doping level, the regions are:

The magnetic flux in a coil of 100 turns increases by 12 × 10³ Maxwell in 0.2 second due to the motion of a magnet. The emf induced in the coil will be.

Which of the following is not a consequence of Gauss’s law?

A 10   capacitor and a 20  capacitor are connected in series across a 200 V supply line. The charged capacitors are then disconnected from the line and reconnected with their positive plates together and negative plates together and no external voltage is applied. What is the potential difference across each capacitor

(a)

(b)

(c) 400 V

(d) 200 V