Course

O Level Physics: Electricity and Magnetism (5054)

Name: O Level Physics: Electricity and Magnetism (5054)
Price: 1299 BDT

The whole of 5054 section 4, from magnets and charge to circuits, safe mains electricity, motors, induction, transformers and the oscilloscope.

72 lessons11h 31mEnglish

What you'll learn

Explain magnets, charge, current and circuits in plain words, with the right diagram
Calculate with charge, current, e.m.f., potential difference, resistance, power, energy and cost
Use the hand rules for fields, forces and induction, and apply the transformer equations

Requirements

Basic algebra and graph reading
The 5054 mechanics and thermal physics course is helpful but not required

Course content

72 lessons · 11h 31m

4.1 · Simple magnetism and magnetic fields

Poles and the forces between them, magnetic and non-magnetic materials, induced magnetism, field lines and how to plot them, soft iron and steel, and what magnets are used for.

0/9

Magnets and magnetic materials

Every magnet has a north and a south pole. Like poles repel, unlike poles attract, and only some metals are magnetic.

Preview10m 2.

Induced magnetism

A magnet turns a nearby iron nail into a magnet, with the opposite pole at the near end. That is why it is attracted.

Preview10m

Magnetic fields and field lines

A field is the space where a pole feels a force. Lines go from N to S, and close lines mean a strong field.

10m

Plotting magnetic field lines

Use a plotting compass or iron filings to draw the field round a bar magnet and between two magnets.

10m

Temporary and permanent magnets

Soft iron is easy to magnetise and loses it at once. Steel is harder to magnetise and keeps it.

10m

Uses of permanent magnets and electromagnets

A fridge door needs a magnet that stays on. A crane needs one it can switch off. Match each magnet to its job.

10m

Simple magnetism: practice

A timed drill of mixed questions: poles, induced magnetism, field lines, soft iron and steel.

Simple magnetism: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

Simple magnetism: summary

The key points and common mistakes on one screen, with cards to revise from.

4.2.1-4.2.4 · Electrical quantities

Charge and electric fields, current and how to measure it, e.m.f. and potential difference, resistance, current-voltage graphs and what decides the resistance of a wire.

0/15

Electric charge

Rub a balloon on your hair and electrons move. Like charges repel and unlike charges attract.

Preview14m 2.

Conductors and insulators

Metals have free electrons, so charge moves through them. Plastic holds its electrons tightly.

Preview12m

Electric fields

A charge feels a force in an electric field. The field points the way a positive charge is pushed.

14m

Electric current

Current is the charge passing a point each second: I = Q/t. Electrons drift one way, conventional current points the other.

14m

Measuring current with an ammeter

An ammeter goes in series. Start on the biggest range, then choose the range that gives the most precise reading.

14m

Direct current and alternating current

A cell pushes charge one way (d.c.). The mains supply reverses direction 100 times a second (a.c.).

12m

Electromotive force (e.m.f.)

The e.m.f. of a source is the energy it gives each coulomb of charge that goes round the circuit: E = W/Q.

10m

Potential difference and voltmeters

The p.d. across a component is the energy each coulomb gives to it: V = W/Q. A voltmeter goes in parallel.

10m

Resistance

Resistance tells you how hard it is to push current through a component: R = V/I, measured in ohms.

10m

10.

Measuring resistance

An ammeter in series and a voltmeter in parallel give I and V. Divide to find R, and repeat to check.

15m

11.

Current-voltage graphs

A resistor gives a straight line, a filament lamp curves over as it heats, and a diode lets current through one way only.

10m

12.

Resistance of a wire: length and cross-sectional area

Double the length and the resistance doubles. Double the cross-sectional area and it halves.

10m

13.

Electrical quantities: practice

A timed drill of mixed questions: charge, current, e.m.f., p.d., resistance and graphs.

14.

Electrical quantities: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

15.

Electrical quantities: summary

The key points, formulas and common mistakes on one screen, with cards to revise from.

4.3.1-4.3.3 · Electric circuits

Circuit symbols, current and potential difference in series and parallel circuits, combined resistance, potential dividers, and thermistors and LDRs as sensors.

0/10

Circuit diagrams and circuit components

Each component has a symbol. Learn them, then read and draw a circuit the way an examiner expects.

Preview10m 2.

Series circuits: current and potential difference

One path: the current is the same everywhere, and the p.d.s across the parts add up to the supply.

Preview10m

Combined resistance in series

Resistors in series add: R = R1 + R2. The pair is always bigger than either one.

10m

Parallel circuits: current and potential difference

Every branch gets the full p.d., and the branch currents add up to the current from the supply.

10m

Combined resistance in parallel

A second path makes it easier for current to flow, so two resistors in parallel have less resistance than either.

10m

Potential dividers

Two resistors in series share the supply p.d. in the ratio of their resistances: V1/V2 = R1/R2.

10m

Thermistors and light-dependent resistors

A thermistor responds to temperature and an LDR to light. In a potential divider, they make a sensor.

10m

Electric circuits: practice

A timed drill of mixed questions: symbols, series and parallel rules, combined resistance and sensors.

Electric circuits: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

10.

Electric circuits: summary

The key points, formulas and common mistakes on one screen, with cards to revise from.

4.4.1-4.4.2 · Practical electricity

What electricity does at home, power and energy (P = IV, E = IVt), the kilowatt-hour and the bill, and how live, neutral, earth, fuses and circuit breakers keep people safe.

0/11

Uses of electricity: heating, lighting and motors

A kettle heats, a lamp lights, a fan turns. Each one changes electrical energy into something useful.

Preview10m 2.

Electrical power

Power is energy transferred each second. For an electrical appliance, P = IV.

Preview10m

Electrical energy

Energy is power multiplied by time: E = IVt. A kettle on for longer uses more energy.

10m

The kilowatt-hour and the cost of electricity

One kilowatt-hour is 1 kW used for 1 hour. Multiply the units by the price to find the bill.

10m

Electrical hazards

Damaged insulation, hot cables, water and overloaded sockets can cause shocks and fires.

10m

Mains wiring: live, neutral and earth

The live wire carries the high voltage, so the switch and the fuse must be in the live wire.

10m

Fuses and circuit breakers

A fuse melts and a circuit breaker trips when the current is too big. Choose a rating just above the normal current.

10m

Earthing and double insulation

An earth wire gives a fault current an easy path to the ground, so the fuse blows before anyone touches the case.

10m

Practical electricity: practice

A timed drill of mixed questions: power, energy, cost, fuse ratings and safe wiring.

10.

Practical electricity: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

11.

Practical electricity: summary

The key points, formulas and common mistakes on one screen, with cards to revise from.

4.5.3-4.5.5 · Magnetic effect of a current, forces and the d.c. motor

The field round a wire and a solenoid, relays and loudspeakers, the force on a current in a magnetic field, beams of charged particles, and how a d.c. motor keeps turning.

0/11

Magnetic field of a straight wire

A current makes circles of field round a wire. Grip the wire with your right hand to find their direction.

Preview10m 2.

Magnetic field of a solenoid

Wind the wire into a coil and the field looks like a bar magnet. More current or more turns make it stronger.

Preview10m

Relays

A small current in a coil pulls an iron switch closed, so a small circuit can safely switch a big one.

10m

Loudspeakers

A changing current in a coil next to a magnet pushes a cone in and out, and the cone makes sound.

10m

Force on a current-carrying conductor

A wire carrying a current across a magnetic field is pushed sideways. Fleming’s left-hand rule gives the direction.

10m

Force on beams of charged particles

A beam of electrons is a current too, so a magnetic field bends it. Point the current finger the opposite way to the electrons.

10m

Turning effect on a current-carrying coil

The two sides of a coil are pushed opposite ways, so the coil turns. More turns, more current or a stronger field turn it harder.

10m

The d.c. motor

A split-ring commutator reverses the current every half turn, so the coil keeps turning the same way.

10m

Magnetic effect of a current: practice

A timed drill of mixed questions: field patterns, the right-hand grip rule, the left-hand rule, relays and motors.

10.

Magnetic effect of a current: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

11.

Magnetic effect of a current: summary

The key points, rules and common mistakes on one screen, with cards to revise from.

4.5.1-4.5.2, 4.5.6, 4.6 · Electromagnetic induction, the transformer and the oscilloscope

How a moving magnet makes a current, which way it flows, the a.c. generator, how a transformer changes voltage, why the grid uses high voltage, and reading an oscilloscope.

0/10

Electromagnetic induction

Move a magnet in a coil and the meter moves. Faster, stronger or more turns make a bigger e.m.f.

Preview10m 2.

Direction of an induced e.m.f.

The induced current always opposes the change that makes it. Fleming’s right-hand rule gives its direction.

Preview10m

The a.c. generator

A coil turning in a field makes an e.m.f. that rises, falls and reverses. Slip rings carry it out.

10m

The transformer

Two coils on one iron core. The turns ratio sets the voltage ratio: Vp/Vs = Np/Ns.

10m

Power in a transformer

A perfect transformer gives out the power it takes in: IpVp = IsVs. Step the voltage up and the current goes down.

10m

High-voltage transmission of electricity

A higher voltage means a smaller current, and the power lost in the cables, I²R, falls a lot.

10m

Using an oscilloscope

Count squares, then multiply by the Y-gain for voltage and by the timebase for time.

10m

Electromagnetic induction: practice

A timed drill of mixed questions: induction, generators, transformers, transmission and oscilloscope readings.

Electromagnetic induction: exam practice

Exam-style questions with marks, mark schemes and full worked solutions.

15m

10.

Electromagnetic induction: summary

The key points, formulas and common mistakes on one screen, with cards to revise from.

About the creator

8bitlesson

Cambridge O Level, A Level and university courses, taught through interactive labs.

Mentora builds the sciences and mathematics as things you can move rather than videos you watch. Cambridge O Level and A Level mathematics, physics, chemistry and accounting, a primary mathematics track, and first-year university computer science. Every lesson works a real exam question end to end.