Category: A- Magnetism

Magnetism (A-level revision questions with answers)

07/11/2021 0

1. (a)(i) Write down an expression for the force on a charge, q coulombs moving with velocity, u, at an angle, α, to a uniform ... Read More

Explain why a current carrying conductor placed in a magnetic field experience a force

06/26/2021 0

Explain why a current carrying conductor placed in a magnetic field experience a force The current in the wire setup a magnet field around the ... Read More

Explain the main precautions taken in the construction of an a.c. transformer

06/26/2021 0

Explain the main precautions taken in the construction of an a.c. transformer Low resistance copper wire are used to reduce I2R losses. Laminated core reduce ... Read More

Explain the application of eddy currents

06/26/2021 0

Explain the application of eddy currents. (03marks) Damping a 'galvanometer. In the galvanometer the coil is wound on a metal former. Eddy currents in the ... Read More

Explain how eddy currents can be produced. 

06/26/2021 0

Explain how eddy currents can be produced.  Eddy currents are currents induced in a conductor moving across magnetic field; these currents oppose the motion of ... Read More

Explain why an alternating current apparently flow through a capacitor whereas a direct current does not.

06/26/2021 1

Explain why  an alternating current apparently flow through a capacitor whereas a direct current does not. When a capacitor is connected to a d.c source, ... Read More

Derive an expression for the charge, Q, induced in a coil of N turns when the magnetic flux through it changes

06/26/2021 0

Derive an expression for the charge, Q, induced in a coil of N turns when the magnetic flux through it changes   Please Subscribe to ... Read More

Describe with the aid of a diagram, an absolute method of determining resistance

06/26/2021 0

Describe with the aid of a diagram, an absolute method of determining resistance The circuit is connected as above. The metal disc of known radius ... Read More

State one advantage of a.c over d.c

06/26/2021 0

State one advantage of a.c over d.c c can easily and cheaply be changed from one voltage to another. c can easily be transmitted with ... Read More

Explain why the primary current in the a.c. transformer increases when the secondary coil is connected to the load?

06/26/2021 0

Explain why the primary current in the a.c. transformer increases when the secondary coil is connected to the load?  When a load is connected to ... Read More

How can hysteresis loss be minimized in a.c. transformer?

06/26/2021 0

How can hysteresis loss be minimized in a.c. transformer? It is minimized by using soft magnetic materials like soft iron and perm alloy in which ... Read More

(iii) Explain why on average the power delivered to the inductor in one cycle is zero.

06/26/2021 0

Explain why on average the power delivered to the inductor in one cycle is zero. During the first quarter cycle, when current increases, work is ... Read More

Explain why the voltage at a generating power station must be stepped up to very high value for long distance transmission

06/26/2021 0

Explain why the voltage at a generating power station must be stepped up to very high value for long distance transmission At high voltage current ... Read More

Describe how the damping can be reduced in ballistic galvanometer

06/26/2021 0

Describe how the damping can be reduced in ballistic galvanometer Damping in ballistic galvanometer is reduced in the following ways Winding the coil on non-conducting ... Read More

State why the damping in the ballistic galvanometer should be as small as possible.

06/26/2021 0

State why the damping in the ballistic galvanometer should be as small as possible. When the oscillation in the ballistic galvanometer is damped, the deflection ... Read More

What is a Weber?

06/26/2021 0

What is a Weber? The weber is magnetic flux that passes normally though an area of 1m2. When the magnetic flux density is 1T. Please ... Read More

Explain why a moving coil ammeter is unsuitable for measuring alternating current

06/26/2021 0

Explain why a moving coil ammeter is unsuitable for measuring alternating current.  When an a.c is passed through a moving coil ammeter, the direction of ... Read More

Explain how an alternating current can be measured using a rectifier meter

06/26/2021 0

Explain how an alternating current can be measured using a rectifier meter When a.c is supplied to a rectifier meter, current flows in only one ... Read More

Describe an experiment which can be used to demonstrate self-induction

06/26/2021 0

Describe an experiment which can be used to demonstrate self-induction An iron cored coil is connected in series with a bulb, cell and switch as ... Read More

Explain why a current carrying conductor placed in a magnetic field experiences a force

06/26/2021 0

Explain why a current carrying conductor placed in a magnetic field experiences a force The current sets up magnetic field around the wire. When the ... Read More

Sketch on the same axes the variation with time of the voltage and current is a capacitor is connected to the voltage supply and explain your graph

06/26/2021 0

Sketch on the same axes the variation with time of the voltage and current is a capacitor is connected to the voltage supply and explain ... Read More

Show that when an inductor s connected to an a.c supply voltage of V = V0sin2πft, the resulting current lags the voltage by 900.

06/26/2021 0

Please Subscribe to promote this website. Subscription is free Share with a friend We value your comments Thank you so much Read More

Magnetism (A-level) notes

06/12/2021 0

Magnetism It refers to physical phenomena arising from the force caused by magnets, objects that produce fields that attract or repel other objects. Magnetism is ... Read More

Electromagnetic Induction

05/30/2021 0

Electromagnetic Induction If  a wire is moved through a magnetic field in such a way that it cuts the  magnetic lines of force, a voltage ... Read More

Moving coil loud speaker (physics)

05/30/2021 0

Moving coil loud speaker When the varying current is supplied into the coil, the coil is magnetized and vibrates backwards and forwards, with the same ... Read More

Mode of action  telephone receiver (physics)

05/30/2021 0

Mode of action  telephone receiver (physics) The varying current from the microphone passes through the coil of electromagnets, soft iron gets magnetized and pull the ... Read More

Electric bell

05/30/2021 0

Electric bell When the switch is closed, current flows through the circuit and the core become magnetized The iron armature is attracted towards the magnetized ... Read More

Magnetic field pattern due to solenoid

05/30/2021 0

Magnetic field pattern due to solenoid Please Subscribe to promote this website. Subscription is free Share with a friend Your comments are highly welcome Thank ... Read More

Magnetic field pattern due to parallel conductors

05/30/2021 0

Magnetic field pattern due to parallel conductors   Please Subscribe to promote this website. Subscription is free Share with a friend Your comment is valuable ... Read More

Magnetic field pattern due to a coil

05/30/2021 0

Magnetic field pattern due to a coil Please Subscribe to promote this website. Subscription is free Share with a friend Your comment is valuable Your ... Read More

Magnetic field on straight conductor carrying current into or out of the paper

05/30/2021 0

Magnetic field pattern on straight conductor carrying current into or out of the paper Please Subscribe to promote this website. Subscription is free Share with ... Read More

Magnetic flux pattern due to soft iron in earth’s horizontal magnetic field

05/30/2021 0

Magnetic flux pattern due to soft iron in earth’s horizontal magnetic field Please Subscribe to promote this website. Subscription is free Share with a friend ... Read More

Magnetic flux pattern of a horizontal bar magnet in earth’s magnetic field

05/30/2021 0

Magnetic flux pattern of a horizontal bar magnet in earth’s magnetic field South Pole, S, of bar magnet facing to north (attraction occurs) North Pole, ... Read More

Experiment to determine magnetic meridian

05/30/2021 0

Experiment to determine magnetic meridian A permanent bar magnet is suspended on a retort stand using a thread and allowed to settle. The vertical plane ... Read More

An experiment to determine the magnetic field pattern of bar magnet using iron fillings.

05/30/2021 0

An experiment to determine the magnetic field pattern of bar magnet using iron fillings. A cardboard is placed on a magnet and iron fillings sprinkled ... Read More

Soft  and hard magnetic substances

05/30/2021 0

Soft  and hard magnetic substances Soft magnetic materials are substance that are easily magnetized and easily lose magnetism, e.g. soft iron. Soft magnetic materials are ... Read More

Storing magnets

05/30/2021 0

Storing magnets Small pieces of soft iron called keepers are placed across opposite poles of two bar magnets These iron keepers become induced magnets and ... Read More

Methods of demagnetization

05/30/2021 0

Demagnetization Demagnetization is the process through which magnets lose their magnetism Demagnetization result in scattering molecular magnets to face in randomly.   Methods of demagnetization ... Read More

Magnetic saturation

05/30/2021 0

Magnetic saturation This is the maximum level of magnetization when the resultant magnetic axes of all domains in magnetic material are aligned with the magnetizing ... Read More

Magnetization or methods of making a magnet

05/30/2021 0

Magnetization This is a process by which randomly arranged molecular magnet of a ferromagnetic material are arranged to point in one direction.  Methods of magnetization ... Read More

Magnetic domain theory

05/30/2021 0

Magnetic domain theory A magnet is made us of tiny molecular magnets called dipole arranged in groups called magnetic domains, lined up with their N-poles ... Read More

How to test for polarity of am magnet

05/30/2021 0

Testing for polarity of a pole A known pole of magnet is brought near the ends of a material suspected to be a magnet. If ... Read More

Laws of magnetism

05/30/2021 0

Laws of magnetism Like poles of magnets repel; g. when a north pole is brought near a north pole or a south pole brought near ... Read More

What are uses of magnets

05/30/2021 0

Uses of magnets In construction of cycle dynamos, telephones, loud speaker, electric meters, current measuring instruments. To remove metal splinters from oil engine For door ... Read More

What is magnetism?

05/30/2021 0

Magnetism is the ability of substances to attract and/or repel others Please Subscribe to promote this website. Subscription is free Share with a friend Your ... Read More

(ii) Sketch graphs to show the time-dependence of supplied voltage and the current in the circuit.

05/29/2021 0

Sketch graphs to show the time-dependence of supplied voltage and the current in the circuit. Please Subscribe to promote this website. Subscription is free Share ... Read More

Discuss the factors which determine the maximum e.m.f generated by a dynamo.

05/29/2021 0

Discuss the factors which determine the maximum e.m.f generated by a dynamo. Induced e.m.f, E = 2πfNBAsin 2πft Maximum e.m.f, E0 = 2πfNBA Thus maximum ... Read More

Give two practical applications of this Eddy currents

05/29/2021 0

Give two practical applications of this Eddy currents damping of moving coil meters melting metals in induction furnaces breaking in electric train   Please Subscribe ... Read More

Explain the term back e.m.f in a d.c motor.

05/29/2021 0

Explain the term back e.m.f in a d.c motor. As the motor rotates the magnetic field, the flux linking changes. This induces an e.mf in ... Read More

Explain the advantages of a.c over d.c in power transmissions

05/29/2021 0

Explain the advantages of a.c over d.c in power transmissions c can easily be stepped up and down c is easy to generate c can ... Read More

Describe an experiment to demonstrate mutual induction

05/29/2021 0

Describe an experiment to demonstrate mutual induction Coil A and B are placed close to each other. When K is closed bulb P lights. Hence ... Read More

Describe how you would determine the value of the earth’s magnetic flux density at a place, using a search coil.

05/29/2021 0

A coil of known number of turns, N (about 100) and area A is connected to a calibrated ballistic galvanometer so that the total resistance ... Read More

What is hysteresis loss ? 

05/29/2021 0

What is hysteresis loss ?  Hysteresis loss is the loss in energy due to the magnetic domains from one direction to the other as current ... Read More

Describe with aid of a labelled diagram the structure and action of a hot wire ammeter.

05/29/2021 0

Describe with aid of a labelled diagram the structure and action of a hot wire ammeter. The current flows through a fine resistance-wire XY, which ... Read More

What is meant by the terms reactance and impedance as applied to alternating currents. 

05/29/2021 0

What is meant by the terms reactance and impedance as applied to alternating currents.  Reactance is non resistive opposition to the flow of a.c in ... Read More

Describe with the aid of a diagram, an absolute method of measuring current.

05/29/2021 0

Describe with the aid of a diagram, an absolute method of measuring current. Current balance is based on principles of moments The apparatus setup is ... Read More

Describe the structure and mode of operation of the repulsion type moving iron meter.

05/29/2021 0

Describe the structure and mode of operation of the repulsion type moving iron meter. When a current is passed through the coil, the iron rods ... Read More