GCSE Physics: Electricity — Deep Revision Workbook

Inside GCSE Physics: Electricity — Deep Revision Workbook

read circuit symbols and the series and parallel rules, calculate charge Q = I × t and potential difference V = I × R (rearranged for R and I), combine resistances and read I–V graphs of the ohmic conductor, filament lamp and diode plus the LDR and thermistor, then work out power P = V × I, P = I² × R and energy E = P × t and E = Q × V, and revise mains electricity, plug safety, static charge and the National Grid’s transformers, before a full exam-style 6-mark question. About 45 minutes.

Learning objectives

• circuit symbols and rules — the ammeter (in series) and voltmeter (in parallel), and how current and potential difference behave in series and parallel circuits;
• charge and Ohm’s law — charge Q = I × t (and I = Q ÷ t), and potential difference V = I × R rearranged for resistance and current;
• resistance and I–V characteristics — resistors in series and parallel, the graphs of an ohmic conductor, a filament lamp and a diode, and the LDR and thermistor;
• power and energy — P = V × I, P = I² × R, E = P × t and E = Q × V;
• mains, static and the National Grid — a.c. at 230 V and 50 Hz, the plug wires, static charge by electron transfer, and step-up and step-down transformers, with a full exam-style 6-mark question.

Activities in this book

1. Section 1 — Circuit Symbols, Series & Parallel

   an ammeter (a circle with the letter A) measures current and is placed in series; a voltmeter (a circle with the letter V) measures potential difference and is placed in parallel across a component. In a series circuit the current is the same everywhere and resistances add; in a parallel circuit the potential difference across each branch equals the supply and the current is shared between the branches.

2. Section 2 — Charge & Ohm’s Law

   charge, current and time are linked by Q = I × t (coulombs, amps, seconds), which rearranges to I = Q ÷ t. Ohm’s law is V = I × R; rearrange it to R = V ÷ I or I = V ÷ R. Always substitute the numbers with units before you calculate.

3. Section 3 — Resistance & I–V Characteristics

   resistors in series add (R_total = R₁ + R₂ + …), while two equal resistors in parallel give a total that is less than either one. An ohmic conductor at constant temperature gives a straight-line I–V graph; a filament lamp curves because its resistance rises as it heats; a diode conducts one way only. An LDR’s resistance falls in brighter light and a thermistor’s resistance falls as it gets hotter.

4. Section 4 — Power, Energy, Mains & the Grid

   electrical power is P = V × I and also P = I² × R; energy transferred is E = P × t and E = Q × V. UK mains is a.c. at about 230 V and 50 Hz, with a live (brown), neutral (blue) and earth (green-and-yellow) wire. When two insulators are rubbed, electrons are transferred, leaving a charge. The National Grid uses a step-up transformer to raise the potential difference for transmission and a step-down transformer to lower it again.

5. Section 5 — Extended Exam-Style 6-Marker

   a 6-mark question rewards clear, linked physics. Plan first: say what each type of transformer does to the potential difference and the current, then link a lower current to less energy wasted in the cables using the idea that power loss depends on the current squared (P = I²R). Use exam keywords — step-up, step-down, potential difference, current, power, dissipated, efficient, alternating.

Suggestions for teaching

• Symbols and meters first. Make sure learners place the ammeter in series and the voltmeter in parallel before analysing whole circuits.
• Drill the equations. Q = It, V = IR, P = VI, P = I²R and E = Pt (and E = QV). Insist on substituting the numbers with units before calculating.
• Rearrange with confidence. Practise V = IR → R = V ÷ I and I = V ÷ R until swapping the subject is automatic.
• Read graphs, not just recall them. Contrast the straight line of an ohmic conductor with the curves of a filament lamp and a diode, and link the LDR and thermistor to sensing circuits.
• Practise the 6-marker. Teach learners to plan marking points (step-up raises pd, current falls, power loss = I²R falls, step-down for safety) before writing full sentences.