⚡ Chapter 16: Electricity – Exercise Short 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 ammeters, direct current vs alternating current, electromotive force, Ohm's law, resistivity, series resistance, and temperature effects on resistance. Each exercise short question is presented with the exact 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.
📖 Exercise Short Questions & Answers (PECTAA 2026)
16.1 How does an ammeter measure electric current?
An ammeter is a device used to measure the current flowing through a circuit. It is connected in series with the circuit so that the entire current passes through it. The current is then indicated by the ammeter. There are two main types of ammeters:
1. Analog ammeter
2. Digital ammeter
An ammeter is a device used to measure the current flowing through a circuit. It is connected in series with the circuit so that the entire current passes through it. The current is then indicated by the ammeter. There are two main types of ammeters:
1. Analog ammeter
2. Digital ammeter
16.2 What is the main difference between direct current and alternating current?
| Direct Current (D.C.) | Alternating Current (A.C.) |
|---|---|
| Direct Current is an electrical current in which the electric charge flows in one direction only. | Alternating Current is a type of current that periodically reverses its direction. |
| In a D.C. circuit, the voltage remains constant over time, and the strength of the current does not change. | A.C. changes direction every 1/50 second, and its frequency is 50 hertz (Hz). |
| Example: Current supplied by a battery. | Example: Electricity produced by power stations. |
16.3 Define electromotive force (e.m.f.).
Electromotive force is the electric potential energy supplied by a battery to a unit positive charge when it flows through the closed circuit.
\[e.m.f = \frac{Energy}{Charge}\]
\[E = \frac{W}{Q}\]
The SI unit of electromotive force is the volt \((V)\).
Electromotive force is the electric potential energy supplied by a battery to a unit positive charge when it flows through the closed circuit.
\[e.m.f = \frac{Energy}{Charge}\]
\[E = \frac{W}{Q}\]
The SI unit of electromotive force is the volt \((V)\).
16.4 State Ohm's law and define resistivity.
Ohm's law: The current flowing through a conductor is directly proportional to the potential difference V across its two ends of a conductor, provided the physical state (dimension, temperature, etc.) of the conductor remains same. Mathematically
\[I \propto V\]
\[V \propto I\]
\[V = IR\]
where \(R\) is the constant of proportionality, and is the resistance of the conductors.
Resistivity: Electrical resistivity \((\rho)\) is a property of a material that indicates how strongly it resists the flow of electric current.
The SI unit of resistivity is ohm-metre \((\Omega m)\).
Ohm's law: The current flowing through a conductor is directly proportional to the potential difference V across its two ends of a conductor, provided the physical state (dimension, temperature, etc.) of the conductor remains same. Mathematically
\[I \propto V\]
\[V \propto I\]
\[V = IR\]
where \(R\) is the constant of proportionality, and is the resistance of the conductors.
Resistivity: Electrical resistivity \((\rho)\) is a property of a material that indicates how strongly it resists the flow of electric current.
The SI unit of resistivity is ohm-metre \((\Omega m)\).
16.5 What is the formula for calculating the equivalent resistance of resistors connected in series?
The formula for calculating the equivalent resistance of resistors connected in series is:
\[R_{e} = R_{1} + R_{2} + R_{3}\]
The formula for calculating the equivalent resistance of resistors connected in series is:
\[R_{e} = R_{1} + R_{2} + R_{3}\]
16.6 How does temperature affect the resistance of a conductor?
Effect on Conductors (Metals): The resistance and resistivity of a conductor change with temperature. In most conductors (metals), resistance increases with an increase in temperature because the increased vibration of atoms makes it more difficult for electrons to flow.
Effect on Semiconductors: In semiconductors, resistance decreases as the temperature increases. This is because an increase in temperature releases more free charge carriers, which increases conductivity and reduces resistance.
Effect on Conductors (Metals): The resistance and resistivity of a conductor change with temperature. In most conductors (metals), resistance increases with an increase in temperature because the increased vibration of atoms makes it more difficult for electrons to flow.
Effect on Semiconductors: In semiconductors, resistance decreases as the temperature increases. This is because an increase in temperature releases more free charge carriers, which increases conductivity and reduces resistance.
📐 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, define key terms precisely, mention formulas with units, and relate to real-life examples. These exercise questions follow the PECTAA 2026 pattern and are prepared by Subject Specialist Muhammad Tayyab.
Created by Hira Science Academy | Aligned with PECTAA 2026 Syllabus