Electric Charges and Fields — Physics STD 12 Science — Question

When a negatively charged conductor is connected to earth

The sum of binary numbers 1011 and 110 is :

Two insulated metallic spheres of 3 μF  and 5 μF capacitances are charged to 300 V and 500V respectively. The energy loss, when they are connected by a wire is

(a) 0.012 J

(b) 0.0218 J

(c) 0.0375 J

(d) 3.75 J

1000 small water drops each of radius r and charge q coalesce together to form one spherical drop. The potential of the big drop is larger than that of the smaller drop by a factor of

(a) 1000

(b) 100

(c) 10

(d) 1

Mass of earth has been determined through

(a) Use of Kepler's  constancy law

(b) Sampling the density of earth's crust and using R

(c) Cavendish's determination of G and using R and 'g' at the surface

(d) Use of periods of satellites at different heights above earth's surface

The magnetic induction in the region between the pole faces of an electromagnet is 0.7 weber/m². The induced e.m.f. in a straight conductor 10 cm long, perpendicular to B and moving perpendicular both to magnetic induction and its own length with a velocity 2 m/sec is

(a) 0.08 V

(b) 0.14 V

(c) 0.35 V

(d) 0.07 V

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

A plane wavefront (λ = 6   falls on a slit 0.4 mm  wide. A convex lens of focal length 0.8 m  placed behind the slit focusses the light on a screen. What is the linear diameter of second maximum

(a) 6mm

(b) 12 mm

(c) 3 mm

(d) 9 mm

In what form is energy present in the capacitor?

If the capacitors in the previous question are joined in parallel, the capacitance and the breakdown voltage of the combination will be:

1. 2C and 2V
2. C and 2V
3. 2C and V
4. C and V