Two balls carrying charges - and +8 attract each other with a force F. If a charge of -3 is added to both the balls, then the force between then will become
A. 2F
B. F/2
C. F
D. zero
A. 2F
B. F/2
C. F
D. zero
C. F
The force between two charges, when placed in free space, is 5N. if they are in a medium of relative permittivity 5, the force between them will be
A. 1N
B. 25N
C. 2.5N
D. 1/5N
the magnitude of a charge q at the center of two equal and like charges Q so that the three charges are in equilibrium
A. Q
B. Q/2
C. Q/4
D. –Q/4
Two-point charges 2μC and 4μC are placed 2 cm apart. The ratio of the Coulomb’s force experienced by them is
(A) 1: 2
(B) 2: 1
(C) 1: 1
(D) 4: 1
A point charge +Q is placed in the vicinity of a conducting surface. Draw the electric field lines between the surface and the charge.
If a charge q is placed at the center of the line joining two equal charges Q such that the system is in equilibrium, then the value of q is
(A)Q/2
(B)-Q/2
(C)Q/4
(D)-Q/4
Figure shows a point charge + Q, located at a distance R/2 from the centre of a spherical metal shell. Draw the electric field lines for the given system.
Two charges q and –3q are placed on x-axis separated by distance d. Where a third charge 2q should be placed such that it will not experience any force ?
The direction of magnetic dipole moment is always from
a) North pole to south pole
b)Away from North pole outside magnet
c) South pole to North Pole
d) all of the above
The condition for Fraunhoffer diffraction from a single slit is that the light wave-front incident on a slit should be
(A) Spherical
(B) Cylindrical
(C) Plane
(D) Rectangular
A torch bulb rated as 4.5 W, 1.5 V is connected as shown in the figure. The emf of the cell needed to make the bulb glow at full intensity is
(a) 4.5 V
(b) 1.5 V
(c) 2.67 V
(d) 13.5 V
Electric flux emanating through a surface element placed in an electric field is
(A) 10 units
(B) 20 units
(C) 4 units
(D) 16 units
A vertical disc of radius 10 cm makes 10 revolutions per second about a horizontal axis passing through its centre. A uniform magnetic field 10⁻² T acts perpendicular to the plane of the disc. The potential difference between its centre and rim in volts is
(a) 3.14 × 10⁻² V
(b) 3.14 × 10⁻³ V
(c) 6.28 × 10⁻² V
(d) 6.28 × 10⁻³ V
The insulation property of air, breaks down at E=3x \(10^6\)V/m. The maximum charge that can be given to a sphere of radius 2.5 m is approximately
(A) 2x \(10^{-2}\)C
(B) 2x \(10^{-3}\)C
(C) 3x \(10^{-6}\)C
(D) 3x \(10^{-5}\)C
A parallel plate air capacitor has a capacitance 18μF. If the distance between the plates is tripled and a dielectric medium is introduced, the capacitance becomes 72μF. The dielectric constant of the medium is
(a) 4
(b) 9
(c) 12
(d) 2