Physics Mock Test- 4 - Class 10 MCQ

The correct answer is B as e electric current through the copper wire has produced a magnetic . In 1820 he accidentally discovered that a compass needle got deflected ... Through this observation Oersted showed that electricity and . representing the magnetic field around a current-carrying straight wire.

The magnetic field around a straight current carrying conductor or wire can be increased by bending the wire into circular loop. A circular loop is made up of large number of very small straight wires.A magnetic field is produced by an electric current flowing through a circular coil of wire.Each small section of current carrying wire contributes to magnetic field lines. At the centre of circular wire,field lines become straight and perpendicular to the plane of coil.Right hand thumb rule is used to determine the direction of magnetic field produced due to current carrying circular wire.

When current flows through a straight conductor, it is said that the current is straight. The magnetic field produced due to a straight current carrying conductor is in the form of concentric circles. The centre of the circles lies on the conductor itself and are in the plane perpendicular to the straight conductor. This implies that the magnetic field produced due to straight current is circular.

A concave mirror forms a real and inverted image larger than the object size when object is situated between principal focus (F) and centre of curvature (C) of the mirror

When source of light is placed verg near to the focus of the reflector which are concave in shape, the reflected light becomes parallel to the principal axis.

When a linear object is placed at a distance equal to focal length of a convex mirror then its virtual image is form ed behind the mirror at a distance f/2 
As per sign convention u = - f and focal length o f convex mirror is + ve, hence from mirror formula we have 
  or   or 

A voltmeter is an instrument used for measuring the electrical potential difference between two points in an electric circuit.

Ammeter is used to measure electric current because it has very low resistance and are always connected in series

• Temporary magnetism: Magnets that only have magnetic properties when a current is passing through them are called electromagnets.


• Electromagnets: These magnets are made by wrapping a coil of wire around a magnetic material and passing an electric current through the coil, creating a magnetic field.


• Temporary magnetism: When the current is turned off, the magnetic field disappears, making electromagnets temporary magnets.


• Uses: Electromagnets are used in various applications such as electric bells, magnetic locks, and MRI machines.

• This rule is used to determine the direction of the force acting on a current-carrying conductor placed in a magnetic field.


• According to Fleming's Left Hand Rule, if the forefinger points in the direction of the magnetic field, the thumb points in the direction of the current, then the middle finger indicates the direction of the force acting on the conductor.


• The force is perpendicular to both the direction of the magnetic field and the direction of the current.

• This rule is used to determine the direction of the induced current in a conductor when it moves in a magnetic field.


• According to Fleming's Right Hand Rule, if the forefinger points in the direction of the magnetic field, the thumb points in the direction of motion, then the middle finger indicates the direction of the induced current.


• The rule is based on the principle of electromagnetic induction.

• Lenz's Rule states that the direction of the induced current in a conductor is such that it opposes the change that produced it.


• This rule is based on the law of conservation of energy.


• It helps in determining the direction of the induced current in a conductor when there is a change in the magnetic field.

• Faraday's Law of electromagnetic induction states that a change in magnetic field induces an electromotive force (emf) in a conductor.


• This law explains how a voltage is induced in a conductor when it is exposed to a changing magnetic field.


• It forms the basis for the operation of electric generators and transformers.

• Generator: A generator converts mechanical energy into electrical energy by using the principle of electromagnetic induction. It does not work on the phenomenon of force on a current-carrying conductor in a magnetic field.


• Accelerator: An accelerator is a device used to increase the speed of particles in a particle accelerator. It is not related to the phenomenon described in the question.


• Motor: A motor works on the principle of force on a current-carrying conductor in a magnetic field. When a current-carrying conductor is placed in a magnetic field, a force is exerted on the conductor, causing it to move. This movement is utilized in motors to generate mechanical energy.


• Transformer: A transformer is a device used to transfer electrical energy from one circuit to another through electromagnetic induction. It does not work on the phenomenon of force on a current-carrying conductor in a magnetic field.

As Myopia is a defect of vision in which a person cannot see the distant object clearly. This can be corrected by using the concave lens of appropriate focal length

Let the distance between the object and its real image formed by convex lens be d₁​.
Let the distance of the object from lens be x,so,the image distance from the lens is (d-x)

The minimum distance between an object and its real image in a convex lens is 4f.
hence,option C is correct.
.

As the temperature of a metallic conductor increases, the kinetic energy of the electrons of the conductor also increases
Due to this increase in kinetic energy more obstruction is offered to the flowing electrons i.e. current.
Therefore, as more obstruction is offered to the flowing electrons, the resistance is increased.

When two or more resistors are connected in series, the total resistance of the combination is equal to the sum of all the individual resistances.

Thus, the total resistance of the circuit will always increase.

Given ,v = -3m or -300cm
u = -infinity
f = ?
according to lens formula ,
1/f = 1/v - 1/u
1/f = -1/300 - (-1/infinity)
1/f = -1/300 + 1/infinity
focal length = -300 cm or -3metre
now,
power = 1/focal length(metre)
power = -1/3
power = -0.33 dioptre

Tightening the smart eye band causes the eyeball to elongate, just as squeezing the middle of a peeled hard-boiled egg causes the egg to lengthen. In long-sighted people this pushes the retina backwards, bringing close-up objects back into focus.

A concave lens (also known as a diverging lens) is thinner in the center and thicker at the edges. When light rays pass through a concave lens, they diverge (spread out), causing the rays to appear to come from a single point on the same side of the lens as the object. This results in the formation of a virtual image.

Key characteristics of the image formed by a concave lens:

• Diminished: The image is smaller than the actual object.
• Erect: The image is upright, meaning it has the same orientation as the object.
• Virtual: The image cannot be projected on a screen because the light rays do not actually meet but only appear to do so when extended backward.

Because of these properties, a concave lens always forms a diminished, erect, and virtual image, no matter where the object is placed in front of the lens.

On the other hand, a convex lens (also known as a converging lens) can form different types of images (real and inverted or virtual and erect) depending on the position of the object relative to the lens. But it does not always form a diminished and erect image, unlike the concave lens.

A ray of light passes through optical centre of a lens is refracted back along the same path ie. through optical centre itself.

• Short-circuit: A short circuit occurs when a circuit is created with very low resistance, allowing for a large current to flow.


• Current in the circuit: The current in the circuit at the time of a short-circuit will increase heavily.


• Reasoning: Since the resistance in a short circuit is very low, according to Ohm's Law (V = IR), the current will increase significantly as the resistance approaches zero.


• Effect: This increase in current can lead to overheating, damage to components, and potentially cause a fire hazard.


• Precautions: It is important to protect circuits from short circuits by using fuses, circuit breakers, and proper insulation to prevent accidents.

According to Fleming's Left Hand rule, the direction of force is perpendicular to the direction of magnetic field and current. Here, since the direction of current is taken opposite to the direction of motion of electrons, the force is directed into the page. 

The correct answers are (c) and (d). Each moving charged particle in a magnetic field experiences a force. The direction of force experienced by a positive charge (i.e., a proton) is given by Fleming's left hand rule. The force acting on the proton would change both velocity and momentum.  

In parallel combination, change in length will not be effective, therefore we consider the area of cross-section.
As we know that resistance is inversely proportional to the area of cross-section.

Thus, resistance will decrease with an increase in area of crosssection.

Since electrons are negative they should be repelled by the negative charge and attracted by the positive charge, i.e., in an electric field the electrons must move from regions of low potential to the regions with high potential by the action of the electrical forces.

Electrical resistivity of a given metallic wire depends on number density of free electrons in the conductor which is the nature of material