Electricity: an interactive physics course

Electricity is an interactive electricity physics course that goes from electric charge to wiring a plug safely. Its 24 short sections cover charge, static electricity, electric fields, conductors and insulators, current, potential difference, measuring with ammeters and voltmeters, resistance and Ohm's law, power, paying for electricity, AC and DC, mains plugs, fuses and earthing.

It opens with a battery, a switch and a lamp with live voltage, current and power meters, and builds every idea from there.

What the course covers

Charge and current

Electricity starts with charge: electrons are negative, protons positive, and rubbing materials moves electrons to give static charge. In a metal, some electrons are free to move, and current is how much charge flows past a point each second. One amp is one coulomb per second.

Voltage, resistance and Ohm's law

Potential difference, or voltage, is the energy each coulomb carries: a 12 V battery gives 12 J to every coulomb. Resistance is how strongly something opposes the current, and for a resistor at a steady temperature, current is proportional to voltage, so plotting current against voltage gives a straight line that starts at zero.

Here x is the potential difference in volts and y is the current in amps. At 10 V the current is 2 A, so the resistance is R = V ÷ I = 10 ÷ 2 = 5 Ω.

Power, bills and safety

Power is how fast energy is transferred, in watts, and bills charge for energy in kilowatt-hours: a 2 kW heater on for 3 hours uses 6 kWh. The last sections cover the UK mains supply: the brown live wire carries 230 V AC, the blue neutral completes the circuit, the green and yellow earth protects metal cases, and a fuse melts if the current gets too large.

Try a question from the course

Combine Q = It with E = QV. A lamp draws 0.5 A from a 12 V battery for 60 seconds. The charge through it is Q = 0.5 × 60 = 30 C, and the energy transferred is E = QV = 30 × 12 = 360 J.

Now calculate a current, charge, energy or voltage, then press Mark to check your answer in the course.

Who this course is for

• GCSE physics students revising charge, current, potential difference, resistance, power and mains electricity.
• Students starting electronics or A-level physics who want the basics solid first.
• Anyone who wants to understand their electricity bill and why plugs have fuses.

What you need to know first

The course page suggests Algebra first: you rearrange formulas such as V = IR and P = IV. No electronics knowledge is needed.

How long it takes

There are 24 sections and most take a few minutes. Learners without a plan can open two sections of a course a day, in order, so the whole course takes 12 days. A plan removes the daily limit and lets you go straight to any topic, such as Ohm's law or fuses.

Read next

Physics · Electricity and magnetismCharge equation Q = It: charge, current and timeThe charge equation Q = It, what charge and current are, units, rearranging, charge and energy with E = QV, electrons per coulomb, examples and practice.