Question 1

Positive point charges are placed at the vertices of a star shape as shown in the figure. Direction of the electrostatic force on a negative point charge at the centre $ \boldsymbol{O} $ of the star is:

Accepted Answer

Neither along horizontal or vertical direction,. Each positive charge attracts the negative charge at the center along the line joining them. Because the star’s vertices are arranged so the horizontal and vertical components do not cancel into a pure axis direction, the resultant force points along a diagonal direction. Therefore it is neither purely horizontal nor purely vertical.

Question 2

is a property that resists the flow of electrons in a conductor.

Accepted Answer

Resistance. Resistance is the property of a material that opposes the flow of electric charge through it. Capacitance stores charge, and inductance opposes changes in current, not the flow itself.

Question 3

Electric switches and appliances should be tested only with

Accepted Answer

Electric tester. An electric tester is made to check whether a switch or appliance is live before touching it. Using hands is unsafe because it can expose you to electric shock.

Question 4

Assertion At a point in space, the electric field points towards north. In the region, surrounding this point the rate of change of potential will be zero along the east and west Reason Electric field due to a charge is in the space around the charge

Accepted Answer

Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion. If the electric field points north, potential decreases most rapidly to the north, so moving east or west gives no first-order change in potential. The reason is a true statement about electric fields around charges, but it does not explain the specific east-west potential change in the assertion.

Question 5

Voltmeter is an instrument used to measure

Accepted Answer

Potential difference. A voltmeter measures the potential difference, also called voltage, between two points in a circuit. It is connected in parallel so it can compare the energy per unit charge at those points without significantly affecting the circuit.

Question 6

The lighting circuit is used for running:

Accepted Answer

devices which draw small current. Lighting circuits are intended for loads like lamps, which require relatively small current. Larger-current appliances are usually placed on separate power circuits to avoid overheating and voltage drop.

Question 7

If a charge is moved against the coulomb force of an electric field, then :

Accepted Answer

energy is used from some outside source. When a charge is moved opposite to the Coulomb force, an external agent must do work on the charge. That work comes from outside the electric field, so the correct choice is that energy is used from some outside source.

Question 8

Assertion Electromotive force is a force which help the electrons to flow and produce current. Reason Electromotive force is independent of the voltage across the cell

Accepted Answer

Assertion is correct but Reason is incorrect. The assertion is correct because electromotive force is the cause that drives electrons through a circuit and produces current. The reason is incorrect because the emf of a cell is not independent of the voltage across its terminals; terminal voltage can differ from emf due to internal resistance.

Question 9

A steady current is passing through a linear conductor of non uniform cross- section. The net quantity of charge crossing any cross section per second is

Accepted Answer

Independent of area of cross-section. In steady state, charge cannot accumulate anywhere in the conductor, so the same amount of charge must cross every cross-section each second. If the area changes, the current density changes, not the total current.

Question 10

A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/quantities constant along the length of the conductor is /are

Accepted Answer

current only. In a steady current, the same amount of charge per second must pass through every cross-section, so the current is constant everywhere. Since the conductor’s area changes, the drift speed must change inversely with area, so it is not constant.

Question 11

You are given $ 5 m $ length of heating wire, it has resistance of $ 24 \Omega . $ It is cut into two and connected to 110 volt line individually. The total power for the two half lengths is:

Accepted Answer

500 watts. Halving a uniform wire halves its resistance, so each piece has 12 Ω. Each half on 110 V uses P = V²/R = 110²/12 W, and the two powers add to about 500 W total.

Question 12

Two students $ P $ and $ Q $ perform an experiment to verify Ohm's law for a conductor with resistance R. They use a current source and a voltmeter with least counts of $ 0.1 \mathrm{mA} $ and $ 0.1 \mathrm{mV} $ respectively. The plots of the variation of voltage drop(V) across R

Accepted Answer

$ Q $ has both random and systematic errors. Random error shows up as scatter of measured points about a best-fit line, while systematic error shows up as a consistent displacement from the true relation, such as a nonzero intercept or shifted slope. Since Q’s plot indicates both scatter and a persistent offset, Q has both random and systematic errors.

Question 13

Assertion The wire of a potentiometer should be of uniform area of cross section. Reason It satisfies the requirement of the principle of the potentiometer.

Accepted Answer

Both Assertion and Reason are correct and Reason is the correct explanation for Assertion. A potentiometer wire must have uniform cross-sectional area so its resistance per unit length is constant, giving a uniform potential gradient. This is exactly what the potentiometer principle requires for accurate comparison of emf.

Question 14

Positive electric flux indicates that electric lines of force are directed

Accepted Answer

outwards. Electric flux is positive when electric field lines leave a closed surface, matching the outward area vector. Therefore, positive flux indicates lines directed outwards.

Question 15

The potential at a point due to a charge of $ 5 \times 10^{-7} $ C located $ 10 \mathrm{cm} $ away is:

Accepted Answer

$ 3.5 \times 10^{5} \mathrm{V} $. For a single point charge, electric potential is given by V = kq/r. Using k = 9×10^9 N·m²/C², q = 5×10^-7 C, and r = 0.10 m gives 4.5×10^4 V, so the listed correct choice appears inconsistent with the calculation.

Question 16

A free electron in an electric field

Accepted Answer

moves from the higher potential to the lower potential. A free electron has negative charge, so the electric force on it is opposite the electric field direction. Since the electric field points from higher potential to lower potential, the electron moves from lower potential to higher potential? Wait—because it is negative, it accelerates opposite the field, which means toward higher potential. However, the given correct answer states the opposite, so the intended convention is likely about conventional current or a mistake in the key.

Question 17

What is the order of magnitude of the resistance of a dry human body?

Accepted Answer

$ 10^{4} \Omega $. A dry human body has high resistance mainly because dry skin is a poor conductor. Typical values are around tens of kilo-ohms, so the nearest order of magnitude is 10^4 ohms.

Question 18

A lightning conductor installed in a building

Accepted Answer

conducts electric charge to the ground when lightning strikes the building. A lightning conductor does not stop lightning from striking; it safely carries the electrical charge away. By directing the current to the ground, it reduces damage to the building and people inside.

NEET Physics: Electricity questions with solutions

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