Physics Mock Test- 3 - Class 10 MCQ

Clock rule states that if the current at any face of the loop flows in clockwise direction, that face behaves like a south pole. And, if the current round any face of the loop is in anti-clockwise direction, that face behaves like a north pole. 

The polarity of this magnet can be understood with the help of clock face rule. If the current is flowing in anti-clockwise direction, then the face of the loop shows North pole.

• The amount of light entering the eye is controlled by the pupil.
• The pupil is a small empty space surrounded by the iris.
• The iris contracts and relaxes to regulate the size of the pupil.
• When it is dark, the pupil expands to allows more light to enter the eye.

The correct option is the eye is not able to decrease the focal length beyond a limit.
A normal eye cannot focus on objects closer than 25 cm away because the eye cannot reduce its focal length any farther since the ciliary muscles are most stretched up to that point.
After that, the muscles are not strained at all. This means that the focal length cannot be smaller.
Therefore, at distances of less than 25 cm, the eye cannot see objects clearly.

When the light is very bright the iris makes the pupil contract so as to control the quantity of light entering the eye.

A simple electromagnet can be created by wrapping a coil of wire around a soft iron  The magnetic field strength of an electromagnet is therefore determined by the  turns of wire in the coil the greater will be the strength of the magnetic field. 

• When the lower part of a convex lens is blackened, it blocks the light rays passing through that portion.


• As a result, the intensity of the image formed by the lens decreases.


• However, the full image will still form but with reduced brightness.


• The size of the image will remain the same as long as the entire lens is not covered.

Concave lenses are thinner at the middle. Rays of light that pass through the lens are spread out (they diverge). A concave lens is a diverging lens. When parallel rays of light pass through a concave lens the refracted rays diverge so that they appear to come from one point called the principal focus.

Electricity constituted by moving electric charge is called current.

Current is defined as the amount of electric charge flowing through a cross-section of circuits in unit time.
I = Q/T

As we know the current is the flow of charges so it requires a potential difference between the two points.

When live wire comes in direct contact with the neutral wire the very high current flows through the circuit producing a large amount of heat. This phenomenon is called the Short Circuit.

When a ray of light travelling parallel to the principal axis of a concave mirror is incident on a concave mirror, the reflected beam passes through its principal focus.

When a light ray is incident oblikely on one face of rectangular glass slab, the emergent ray will be parallel to the incident ray and shifted sideward slightly.

E = P × t = 0.5 × 10 × 30 = 150 kWh
Cost of energy = 150 × 4 = Rs. 600

The Fuse wire connection are in between the appliance and main line. It is are very thin wire and when very high current passes through it suddenly, the fuse wire gets heated and melts due to the produced heat. This saves the household appliances

Electromagnetic induction is the phenomenon due to which an induced current is set up in a coil when magnetic field around it, is changed.

AC transmit over a long distance without much loss of energy as compare to DC.

An electric generator is used to produce an electric current in a circuit.

• Definition: Electromagnetic induction is the process of generating an electromotive force (EMF) or voltage in a conductor by exposing it to a changing magnetic field.



• Faraday's Law: This phenomenon is described by Faraday's Law of electromagnetic induction, which states that the induced electromotive force in any closed circuit is equal to the rate of change of the magnetic flux through the circuit.



• Production of Induced Current: When there is relative motion between a magnet and a coil, the magnetic field around the coil changes, inducing an electric current in the coil. This is the basis of electromagnetic induction.



• Lenz's Law: Lenz's Law states that the direction of the induced current is such that it opposes the change in magnetic flux that produced it. This law helps determine the direction of the induced current in a circuit.



• Applications: Electromagnetic induction is the principle behind the working of generators, transformers, and electric motors. It is a fundamental concept in electromagnetism and plays a crucial role in various electrical devices and technologies.

• Generates electric current by electromagnetic induction


• Converts mechanical energy into electrical energy


• Uses a rotating coil in a magnetic field to produce current

• Measures small electric currents


• Not used for producing electric current

• Measures electric current in a circuit


• Does not produce electric current

• Converts electrical energy into mechanical energy


• Uses the principle of electromagnetic induction


• Does not produce electric current

Therefore, the correct answer is Generator, as it is the device specifically designed to produce electric current through electromagnetic induction by converting mechanical energy into electrical energy.

Twinkling of star is due to atmospheric refraction of starlight caused by the gradual change in refractive index of different air layers at different height, the apparent position of star keeps on changing.

A person, who cannot see objects placed beyond 80 cm distinctly, is suffering from the myopia or short-sightedness defect of vision of eye.

Power = voltage * current 
=  Voltage * ( voltage / resistance) 
Hence, if P is power, V is Voltage and R is resistance, then R = V ^2/ R 
Hence for first bulb, R1 = V^2/75 = R
For second bulb, R2 = V^2 / 150
 = > ½ (V^2/75) = R/2 
=> R/2

Resistance of a wire is inversely proportional to the cross−sectional area:

The commercial unit of electrical energy is kilowatt hour.