PHY102: Electricity, Magnetism & Modern Physics TMA1

PHY102: Electricity, Magnetism & Modern Physics TMA1

Instructions: Answer All .
After Submission, you will not be able to answer these questions

Question 1 : What are the dimensions of the constant k in Coulomb’s law of electrostatics?
$$M{L}^3{T}^{-4}{A}^{-2}$$

$$M{L}^2{T}^3{A}^{-2}$$
$$M^{-2}{L}^3{T}^2{A}^{-1}$$
$$M{L}^{2}T-4T-2A-1$$

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Question 2 : A positively charged object repels
neutral objects
both positively and negatively charged objects
positively charged object
negatively charged objects

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Question 3 : Which of the following is a conductor
copper
plastic
silk
glass

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Question 4 : When amber is rubbed with fur
amber is positively charged while fur is negatively charged
amber is negatively charged while fur is neutral
amber is positively charged while fur is neutral
amber is negatively charged while fur is positively charged

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Question 5 : 1 volt is equal to
$$1N/C$$
$$1watt/C$$
$$1J/C$$
$$1J/sC$$

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Question 6 : Which of the following can be used to charge a metal rod that si held in your hand? Rub it with
silk
fur
It cannot be doe
wool

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Question 7 : A tiny ball of mass 0.60 g is suspended from a rigid support with a piece of thread in a horizontal electric field of intensity 700 N/C. The ball is in equilibrium when the thread is inclined at an angle of$${20}_0$$to the vertical. What are the magnitude and sign of the charge on the ball? Take $$g=9.8m/s^2$$
$$3.2\times {10}^{-6}C$$
$$-4.1\times {10}^{-3}C$$
$$-3.1\times {10}^{-6}C$$
$$4.2\times {10}^{-}6C$$

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Question 8 : Calculate the electric field at distance of 320 cm from an infinitely long wire carrying a charge per unit length 8.3 C/m.
$$6.22\times {10}^{10}N/C$$
$$8.85\times {10}^{10}N/C$$
$$3.26\times {10}^{10}\frac{N}{C}$$
$$4.66\times {10}^{10}N/C$$

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Question 9 : Two identical balls balls P and Q, each of mass 0.20 g, carry identical charges and are suspended by two threads of equal length. The balls position themselves at equilibrium such that the angle between the threads is 60_{o}.If the distance between the the balls is 0.5m, find the charge on each of them. Take g = 9.8 m/s^{2}
$$2.3\times {10}^{-}6C$$



$$3.1\times {10}^{-5}C$$
$$1.1\times {10}^{-3}$$C
$$1.8\times {10}^{-}7C$$

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Question 10 : A uniform electric field of 200 N/C is in the x-direction. A point charge of $$3\mu C$$ is released from rest at the origin. What is the kinetic energy of the charge when it is at x = 4 m?
$$1.6\times {10}^{-2}J$$
$$4.8\times {10}^{-2}J$$
$$2.4\times {10}^{-2}J$$
$$3.6\times {10}^{-2}J$$

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Question 11 : Three point charges $$2\mu C,-4\mu C$$, and $6\mu C$ are held at the corners of an equilateral triangle with sides equal to 3 cm.What is the resultant force in newtons on the $2\mu C$ charge?
$$80\vec{i}-69.3\vec{j}$$
$$40\vec{i}-63.7\vec{j}$$
$$-40\vec{i}+63.7\vec{j}$$
$$-80\vec{i}+69.3\vec{j}$$

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Question 12 : The following are true about electric field lines except that they
are discontinuous and may terminate in a vacuum
are drawn such that the magnitude of the field is proportional to the number of lines crossing a unit area perpendicular to the lines
do not intersect one another
give the direction of motion of a unit positive test-charge under the action of the electrostatic force

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Question 13 : Which of the following is not true of an electrostatic force?
it is mutually attractive or repulsive
it obeys an inverse square law
it is weaker than the gravitational attraction between the charged particles.
it acts along the line joining the point charges

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Question 14 : Two charges $$Q_1=500\mu C$$ and $$Q_2=100\mu C$$ are located on the XY plane at the positions $$r_1=3\vec{j}m$$ and $$r_2=4\vec{i}m$$. Find the force exerted on the $Q_2$
$$10.8\vec{i}+14.4\vec{j}N$$
$$14.4\vec{i}–10.8\vec{j}N$$
$$10.8\vec{i}–14.4\vec{j}N$$
$$14.4\vec{i}+10.8\vec{j}N$$

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Question 15 : Which of the following is not true about the electric field intensity $\vec{E}$ of a uniformly charged solid sphere?
$$\vec{E}$$ is directly proportional to the distance from the centre of the sphere
$$\vec{E}$$ is maximum at the surface of the sphere
$$\vec{E}$$ $decreases as a square of the distance from the surface of the sphere
$$\vec{E}$$ decreases as a square of the distance from the centre of the sphere.

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Question 16 : The electric potential difference between two points A and B is 42 V. What is the work done by an external agent in carrying a charge of 5.0$\times {10}^{-5}$ C from A to B at constant speed?
$$21\times 10-4J$$
$$2.1\times {10}^{-3}J$$
$$8.4\times {10}^{-4}J$$
$$8.4\times {10}^{-3}J$$

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Question 17 : From Gauss’ law which of the following is NOT correct?
The electric flux through a Gaussian surface is a vector product of the electric field and a unit vector perpendicular to and outward from the surface
The total electric flux through a cylinder placed in an electric field with its axis parallel to the field is zero
The outward flux of electric field through an enclosed surface is proportional to the electric charges enclosed
The field at a point outside a spherically symmetric charge is the same as the electric field at the same point due to a point charge at its centre.

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Question 18 : Charges of + 2 C and -2 C are situated at points P and Q respectively which are at a distance apart. A point X is mid-way between P and Q. Which of the following correctly describes the electric field and the electric potential at point X?
electric field is toward Q, electric potential is zero
electric field is toward P, electric potential zero
electric field is toward Q, electric potential is negative
electric field is toward P, electric potential is positive

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Question 19 : The term 'lost volts' refers to -----------
energy per coulomb dissipated in the internal resistance of the source of emf
terminal potential difference
energy per coulomb wasted to heat up the connecting wires
energy per coulomb dissipated in the external (load) resistance

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Question 20 : A huge spark due to electric discharge in the atmosphere produces all of the following except
Rapid expansion of surrounding air
Lightning
gamma radiation
shock waves

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