The potential at a point P which is forming a comer of a square of side 93 mm with charges, Q₁ = 33nC, Q₂ = − 51 nC, Q₃ = 47 nC located at the other three comers is nearly

• 16 kV

• 4 kV

• 400 kV

• 160 V

Two equal metal balls are charged to 10 and − 20 units of electricity. Then they are brought in contact with each other and then again separated to the original distance. The ratio of magnitudes of the force between the two balls before and after contact is

• 8 : 1

• 1 : 8

• 2 : 1

• 1 : 2

63.

The electric potential due to a small electric dipole at a large distance r from the centre of the dipole is proportional to

• r

• $\frac{1}{\mathrm{r}}$

• $\frac{1}{{\mathrm{r}}^5}$

• $\frac{1}{{\mathrm{r}}^2}$

In the given circuit the equivalent resistance between the points A and B in ohms is

• 9

• 11.6

• 14.5

• 21.2

In the electric circuit shown each cell has an emf of 2 V and internal resistance of 1Ω. The external resistance is 2Ω. The value of the current I is (in amperes)

• 2

• 1.25 Ω

• 0.4

• 1.2

Which of the following graphs represent variation of magnetic field B with distance r for a straight long wire carrying current ?

If a coil of 40 turns and area 4.0 cm² is suddenly removed from a magnetic field, it is observed that a charge of 2.0 x 10^-4 C flows into the coil. If the resistance of the coil is 80 Ω, the magnetic flux density in Wb/m² is

• 0.5

• 1.0

• 1.5

• 2.0

The maximum value of AC voltage in a circuit is 707 V. Its rms value is

• 70.7 V

• 100 V

• 500 V

• 707 V

The magnetic flux linked with the coil varies with time as  $\mathrm{\varphi }$ = 3 t² + 4 t + 9. The magnitude of the induced emf at 2 s is

• 9 V

• 16 V

• 3 V

• 4 V

An electron enters uniform electric field maintained by parallel plates and of value E Vm^-1 with a velocity v ms^-1 , the plates are separated by a distance d metre, then acceleration of the electron in the field is

• $\frac{\mathrm{Ee}}{\mathrm{m}}$

• $\frac{-\mathrm{Ee}}{\mathrm{m}}$

• $\frac{\mathrm{Ed}}{\mathrm{m}}$

• $\mathrm{Ee}\frac{\mathrm{d}}{\mathrm{m}}$