MCQs of Electric Charges and Electric Fields

Electric Charges and Electric Fields MCQs

MCQs of Electric Charges and Electric Fields

Showing 11 to 20 out of 141 Questions

11.

A charge of 10^-9 C is located at the origin of cartesian co-ordinate system and another charge Q at(2, 0, 0) m. If the X-component of electric field at (3, 1, 1)m is zero, the value of Q = _____

(a)	-0.43 × 10^-9 C
(b)	-4.3 × 10^-9 C
(c)	43 × 10^-9 C
(d)	0.043 × 10^-9 C

12.

Four electric charges +q, +q, -q and -q are respectively placed on the vertices A, B, C and D of a square. The length of the square is a, the intensity of the resultant electric field at the centre is _____

(a)	$\frac{2 \sqrt{2} k q}{a^{2}}$
(b)	$\frac{4 k q}{a^{2}}$
(c)	$\frac{4 \sqrt{2} k q}{a^{2}}$
(d)	$\frac{\sqrt{2} k q}{a^{2}}$

13.

An arc of radius r subtends an angle θ at the centre with the X-axis in a cartesian co-ordinat system. A charge is distributed over the arc such that the linear charge density is λ. Calculate the electric filed at the origin.

(a)	$\frac{k λ}{r} [\sin θ \overset{Λ}{i} + (1 - \cos θ) \overset{Λ}{j}]$
(b)	$\frac{k λ}{r} [- \sin θ \overset{Λ}{i} + (\cos θ - 1) \overset{Λ}{j}]$
(c)	$\frac{k λ}{r} [- \sin θ \overset{Λ}{i} + (1 - \cos θ) \overset{Λ}{j}]$
(d)	$\frac{k λ}{r} [\sin θ \overset{Λ}{i} + (\cos θ - 1) \overset{Λ}{j}]$

14.

Two identically charged spheres are suspended by strings of equal length. When they are immersed in kerosene, the angle between their strings remains the same as it was in the air. Field the density of the spheres.(The dielectric constant of kerosene is 2 and its density is 800 kg m^-3.)

(a)	$400 \frac{k g}{m^{3}}$
(b)	$800 \frac{k g}{m^{3}}$
(c)	$1600 \frac{k g}{m^{3}}$
(d)	$2400 \frac{k g}{m^{3}}$

15.

An electron falls through a distance of 1.5 cm in a space, devoid of gravity, having uniform electric filed of intensity 2.0 × 10⁴ N C^-1 The direction of electric filed intensity is then reversed keeping its magnitude same, in which a proton falls through the same distance. The time taken by both of them are _____

m_e = 9.1 × 10-31 kg, m_p = 1.7 × 10^-27 kg,and e = 1.6 × 10^-19 C

(a)	t_e = 2.9 ns, t_p = 0.13 μs
(b)	t_e = 0.13 ns, t_p = 2.9 μs
(c)	t_e = 2.9 μs, t_p = 0.13 ns
(d)	t_e = 0.13 μs, t_p = 2.9 ns

16.

A charge Q is uniformly distributed on the circumference of a circular ring of radius a. The intensity of electric filed at a point at a distance x from the centre on the axis of the ring is _____

(a)	$\frac{k Q}{(a^{2} + x^{2})^{\frac{3}{2}}}$
(b)	$\frac{x Q}{(a^{2} + x^{2})^{\frac{3}{2}}}$
(c)	$\frac{k x Q}{(a^{2} + x^{2})^{\frac{3}{2}}}$
(d)	$\frac{k Q}{x (a^{2} + x^{2})^{\frac{3}{2}}}$

17.

Three point charges 0.5 μC, -0.25 μC and 0.1 μC are placed at the vertices A, B and C of an equilateral triangle ABC. The length of the side of triangle is 5.0 cm. The resultant force acting on the charge placed at point C _____ k = 9 × 10⁹ MKS.

(a)	0.045 (3, 3) N
(b)	0.050 (3, 3) N
(c)	0.45 (3, 3) N
(d)	4.5 (3, 3) N

18.

The force acting between two point charges kept at a certain distance is Φ. If magnitude of charges are doubled and the distance between them is halved, then the force acting between them is _____ .

(a)	Φ
(b)	4Φ
(c)	8Φ
(d)	16Φ

19.

The surface charge density of a very large surface is -3.0 × 10^-6 Cm ^-2. From what distance should an electron of 150 eV energy be projected towards the plane so that its velocity becomes zero on reaching the plane ? Charge of an elecron = 1.6 × 10^-19C, 1 eV = 1.6 × 10^-19 J, ε₀ = 9 × 10^-12 SI

(a)	9 × 10^-4 cm
(b)	9 × 10^-4 m
(c)	9 × 10^-4 km
(d)	9 × 10⁴ cm

20.

The distance between two point charges 4q and -q is r. A third charge Q is placed at their midpoint. The resultant force acting on -q is zero, then Q = _____ .

(a)	-q
(b)	q
(c)	-4q
(d)	4q

Showing 11 to 20 out of 141 Questions