Category: A- Magnetism
Magnetism (A-level revision questions with answers)
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
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
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
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.
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
An aired cored inductor is connected in series with a switch and d.c. source. The switch is closed and left for some time. Explain why a spark is observed across the switch contacts when the switch is reopened.
An aired cored inductor is connected in series with a switch and d.c. source. The switch is closed and left for some time. Explain why ... Read More
Explain why an alternating current apparently flow through a capacitor whereas a direct current does not.
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
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
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
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?
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?
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.
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
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
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.
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?
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
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
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
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
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
A rectangular coil of N turns each of length, L, and breadth, b, is inclined at an angle θ to a uniform magnetic field of flux density B. Derive an expression for torque of the coil when a current I is passed through it.
A rectangular coil of N turns each of length, L, and breadth, b, is inclined at an angle θ to a uniform magnetic field of ... 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
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.
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
Magnetism It refers to physical phenomena arising from the force caused by magnets, objects that produce fields that attract or repel other objects. The scope ... Read More
Electromagnetic Induction
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)
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)
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
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
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
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
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
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
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
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
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.
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
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
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
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
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
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
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
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
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
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?
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.
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.
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
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.
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
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
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.
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 ?
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.
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.
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.
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
A rectangular coil of N turns, length, L and breadth, b, carrying a current, I, is placed with its plane making a angle, θ, to a uniform magnetic field of flux density, B. Derive the expression for torque exerted on the coil.
A rectangular coil of N turns, length, L and breadth, b, carrying a current, I, is placed with its plane making a angle, θ, to ... Read More
Describe the structure and mode of operation of the repulsion type moving iron meter.
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