amazon.co.ukElectricity and Circuits
A-Level Physics revision: Electricity and Circuits. Learning objectives, key points, worked examples and practice questions across AQA, Edexcel, OCR, WJEC and CCEA.
📌 Key Points
Key Fact: Ohm: V = IR (ohmic) vs non-ohmic (filament, diode); I-V curves
Key Fact: Series: I same, V splits, R_total = ΣR; Parallel: V same, I splits, 1/R_total = Σ1/R
Key Fact: Power: P = IV = I^2R = V^2/R; Energy: E = Pt = IVt
Key Fact: Kirchhoff 1st (junction): ΣI_in = ΣI_out (charge conservation); 2nd (loop): ΣV = 0 (energy conservation)
Key Fact: EMF ε = I(R + r); Terminal PD V = ε - Ir; r = internal resistance
Key Fact: Potential divider: V_out = V_in x R₂/(R₁+R₂); used for sensors
Key Fact: AC: I = I₀sin(ωt), V = V₀sin(ωt+φ); V_rms = V₀/sqrt2, I_rms = I₀/sqrt2
Key Fact: Capacitive reactance Xc = 1/(ωC); Inductive Xl = ωL; Impedance Z = sqrt(R^2+(Xl-Xc)^2)
Key Fact: Resonance: Xl = Xc -> Z_min = R, ω₀ = 1/sqrt(LC)
🎯 Learning Objectives
- Apply Ohm's law and understand I-V characteristics
- Analyse series and parallel circuits with resistors
- Calculate power and energy in DC circuits
- Use Kirchhoff's laws for complex circuits
- Understand internal resistance and EMF of cells
- Analyse potential divider circuits
- Understand AC circuits: RMS values, phase, reactance, impedance
- Use oscilloscopes to measure voltage, frequency, phase
💡 Worked Example
Exam-Style Question
Question: A 12 V battery with internal resistance 0.5 Ω is connected to a 5.5 Ω resistor. Find current, terminal PD, power delivered to load, and power wasted in battery
Model Answer:
Total R = 6 Ω. I = 12/6 = 2 A. Terminal V = IR_load = 2x5.5 = 11 V. P_load = I^2R = 4x5.5 = 22 W. P_battery = I^2r = 4x0.5 = 2 W. Check: P_total = εI = 24 W = 22+2
❓ Practice Questions
Questions:
- Three resistors 2Ω, 3Ω, 6Ω in parallel. Find equivalent resistance
- In a potential divider, V_in=12V, R₁=2kΩ, R₂=4kΩ. Find V_out
- An AC supply 230V RMS, 50Hz. Find peak voltage and period
- A 10 μF capacitor connected to 240V RMS, 50Hz. Find reactance and current
- At resonance, a series RLC circuit has R=10Ω, L=0.1H. Find C and Q-factor
🎬 Video Resources
- Electricity and Circuits - Overview -- YouTube Search
- Electricity and Circuits - Exam Questions -- YouTube Search
📄 Past Papers & Exam Resources
🔗 Further Reading & Resources
- Physics & Maths Tutor - Electricity and Circuits -- Free notes, worksheets, and past paper questions by topic
- Dr Frost Maths - Electricity and Circuits -- Free resources, slides, and interactive questions
- BBC Bitesize - Electricity and Circuits -- BBC Bitesize revision resources