Chapter 1 of Egyptian third-year secondary physics is electric current, Ohm's law and Kirchhoff's two laws, the base for the magnetism, induction and AC chapters that follow. This guide goes through the chapter 1 questions for the 2027 cohort lesson by lesson, with worked examples.
The lessons of chapter 1
- Current, potential difference, resistance and resistivity.
- Resistors in series and in parallel.
- Ohm's law for a closed circuit, with worked examples.
- Kirchhoff's two laws.
- Key formulas and chapter 1 questions.
Worked example: combining resistors
In series, resistances add: 4 + 6 = 10 ohms. In parallel use 1/R = 1/R1 + 1/R2: for 6 and 3 ohms, 1/R = 1/6 + 1/3 = 3/6, so the equivalent is R = 2 ohms, always smaller than the smallest resistor in the group.
Worked example: Ohm's law for a closed circuit
A battery with EMF 12 V and internal resistance 1 ohm is connected to an external resistance of 5 ohms. Current I = EMF ÷ (R + r) = 12 ÷ (5 + 1) = 2 A. The potential difference across the terminals = I × R = 2 × 5 = 10 V, less than 12 V because 1 V is lost inside the battery (2 × 1).
Worked example: Kirchhoff's first law
The currents entering a junction sum to the currents leaving it. If 5 A enters and 2 A leaves in one branch, the other branch carries 5 − 2 = 3 A. The second law says the sum of EMFs around a closed loop equals the sum of (I × R) around it.
Before solving, write down the connection type: series, parallel or closed circuit with internal resistance. Most mistakes come from forgetting the internal resistance or adding parallel resistors as if they were in series.
How EXAMEV helps
The EXAMEV third-year secondary physics bank has 974 questions across eight chapters, 109 of them on chapter 1 alone in five lessons, plus 27 general-review questions. The chapters are: electric current and Kirchhoff, the magnetic effect of current, electromagnetic induction, AC circuits, wave-particle duality, atomic spectra, lasers and modern electronics. Question types: multiple choice, true/false, fill in the blank, short answer, calculations, matching, ordering and advanced questions, each with an explanation. Start with a 25-question practice, then a timed exam of 25 questions in 45 minutes, then the full exam of 50 questions in 100 minutes. For official details about the Thanaweya Amma exam, check the website of Egypt's Ministry of Education.