⚡ Chapter 16: Electricity – Constructed Response Questions
Prepared by Muhammad Tayyab, Subject Specialist Physics, Govt Christian High School Daska. Based on PECTAA 2026 syllabus (National Curriculum 2023).
📖 What's Inside: This chapter covers ammeter and voltmeter connections, resistivity and its effect on current and power, series vs parallel circuits, fuse design, and A.C. vs D.C. transmission. Each constructed response question is presented with the detailed reasoning and exam-ready answer as per the official PECTAA 2026 Physics curriculum. Perfect for Punjab Boards (Lahore, Gujranwala, Multan, etc.) and all BISE boards across Pakistan.
📚 Related Resources – Chapter 16: Electricity
Electricity covers electric current, Ohm's law, resistance, series and parallel circuits, electric power, energy, and household wiring. Includes solved examples and numerical problems.
📖 Constructed Response Questions & Answers (PECTAA 2026)
16.1 Why is it important that an ammeter has very low resistance and is connected in series, while a voltmeter has very high resistance and is connected in parallel? What would happen if they were connected incorrectly?
An ammeter has very low resistance and is connected in series so that it measures the current without affecting it. If connected in parallel, it may cause a short circuit and damage the meter.
A voltmeter has very high resistance and is connected in parallel so that it draws negligible current. If connected in series, it greatly reduces the current, giving incorrect readings and preventing the circuit from working properly.
An ammeter has very low resistance and is connected in series so that it measures the current without affecting it. If connected in parallel, it may cause a short circuit and damage the meter.
A voltmeter has very high resistance and is connected in parallel so that it draws negligible current. If connected in series, it greatly reduces the current, giving incorrect readings and preventing the circuit from working properly.
16.2 If a copper wire is replaced with an aluminum wire of the same dimensions, how would the current and power consumption change in the same circuit? Explain using the concept of resistivity.
According to
\[R = \rho \frac{L}{A}\]
aluminum has a higher resistivity than copper, so it has greater resistance. According to Ohm's law \(\left(I = \frac{V}{R}\right)\), the current decreases. Since
\[P = \frac{V^2}{R}\]
the power consumption also decreases.
According to
\[R = \rho \frac{L}{A}\]
aluminum has a higher resistivity than copper, so it has greater resistance. According to Ohm's law \(\left(I = \frac{V}{R}\right)\), the current decreases. Since
\[P = \frac{V^2}{R}\]
the power consumption also decreases.
16.3 In a household lighting circuit, what practical problems might arise if the bulbs were connected in series instead of parallel?
If bulbs were connected in series:
• If one bulb burns out, all bulbs go OFF.
• The supply voltage is divided, so the bulbs glow dimly.
• Bulbs cannot be controlled independently.
If bulbs were connected in series:
• If one bulb burns out, all bulbs go OFF.
• The supply voltage is divided, so the bulbs glow dimly.
• Bulbs cannot be controlled independently.
16.4 You are tasked with designing a fuse for a device that operates at \(230V\) and \(5A\). What rating would you choose for the fuse and why? What could go wrong if the rating is too low or too high?
A \(6A\) or \(7A\) fuse should be used because it is slightly above the operating current and protects the circuit during an overload.
If the rating is too low, the fuse blows during normal operation. If it is too high, it may not blow during a fault, causing overheating or damage to the device.
A \(6A\) or \(7A\) fuse should be used because it is slightly above the operating current and protects the circuit during an overload.
If the rating is too low, the fuse blows during normal operation. If it is too high, it may not blow during a fault, causing overheating or damage to the device.
16.5 Explain why A.C. is more suitable for power transmission across cities, even though D.C. is used in batteries and portable electronic devices.
A.C. is used for power transmission because it can be stepped up to high voltages and stepped down using transformers, reducing power loss over long distances.
D.C. provides a steady, constant voltage, so it is used in batteries and portable electronic devices.
A.C. is used for power transmission because it can be stepped up to high voltages and stepped down using transformers, reducing power loss over long distances.
D.C. provides a steady, constant voltage, so it is used in batteries and portable electronic devices.
📐 Key Formulas – Electricity
Electric Current: \( I = \frac{Q}{t} \)
Ohm's Law: \( V = IR \)
Series Resistance: \( R_e = R_1 + R_2 + R_3 \)
Parallel Resistance: \( \frac{1}{R_e} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} \)
Electric Power: \( P = IV = I^2R = \frac{V^2}{R} \)
Electrical Energy: \( E = Pt \)
Resistivity: \( R = \rho \frac{L}{A} \)
Unit 10Thermal Physics
Unit 11Transfer of Thermal Energy
Unit 12Waves
Unit 13Sound
Unit 14Light
Unit 15Electrostatics
Unit 16✨ Electricity
Unit 17Electromagnetism
Unit 18Electromagnetic Induction & EM Waves
Unit 19Electronics
Unit 20Atomic and Nuclear Physics
Unit 21Space and Environment
📖 Complete syllabus coverage for Class 10 Physics (PECTAA 2026) – Units 10 to 21
💡 Exam Tip:
For board exams, provide clear reasoning and explain the underlying principles. These constructed response questions follow the PECTAA 2026 pattern and are prepared by Subject Specialist Muhammad Tayyab.
Created by Hira Science Academy | Aligned with PECTAA 2026 Syllabus