Electrostatics — Physics STD 12 Science — Question

There are 8 equal resistances R. Two are connected in parallel, such four groups are connected in series, the total resistance of the system will be

(a) R / 2

(b) 2 R

(c) 4 R

(d) 8 R

Which of the following devices can be used as a square law device for modulation.

A convex mirror is used to form the image of an object. Then which of the following statements is wrong

(a) The image lies between the pole and the focus

(b) The image is diminished in size

(c) The image is erect

(d) The image is real

The length of a wire required to manufacture a solenoid of length l and self-induction L is (cross-sectional area is negligible)

An electron falls from rest through a vertical distance h in a uniform and vertically upward directed electric field E. The direction of electric field is now reversed, keeping its magnitude the same. A proton is allowed to fall from rest in it through the same vertical distance h. The time of fall of the electron, in comparison to the time of fall of the proton is:

Magnetic lines of force

(a) Always intersect

(b) Are always closed

(c) Tend to crowd far away from the poles of magnet

(d) Do not pass through vacuum

Plane figures made of thin wires of resistance R = 50 milli ohm/metre are located in a uniform magnetic field perpendicular into the plane of the figures and which decrease at the rate dB/dt = 0.1 m T/s. Then currents in the inner and outer boundary are. (The inner radius a = 10 cm and outer radius b = 20 cm)

(a) 10– 4 A (Clockwise), 2 × 10– 4 A (Clockwise)

(b) 10– 4 A (Anticlockwise), 2 × 10– 4 A (Clockwise)

(c) 2 × 10– 4 A (clockwise), 10– 4 A (Anticlockwise)

(d) 2 × 10– 4 A (Anticlockwise), 10– 4 A (Anticlockwise)

The vecter term of coulomb's law is :

_______ exists in the region surrounding a magnet, in which force of the magnet can be detected.

A drop of   water carries   charge. What electric field should be applied to balance its weight (assume  

(a) 10 V/m upward

(b) 10 V/m downward

(c) 0.1 V/m downward

(d) 0.1 V/m upward