Electricity is one of the most important scoring topics in the TNPSC General Science syllabus and consistent practice is the key to mastering it. TNPSC Physics Electricity Test 3 brings together carefully selected questions that help you revise electric potential, potential difference, electric current formula, resistance, resistivity, conductivity, factors affecting resistance, conventional current, electron flow, circuit symbols, and combinations of electric cells. Whether you’re preparing for TNPSC Group 4 or any other competitive exam, this quiz is a great way to test your knowledge and improve your confidence.
TNPSC Physics Electricity Test 3 – Detailed Explanations For All Questions
Every question has been followed by a clear and exam-oriented explanation to help you learn the concept behind the correct answer. Instead of simply memorizing facts, spend a few minutes reviewing each explanation carefully. This Electricity Test 3 covers important TNPSC General Science topics such as electric potential, potential difference, electric current formula, resistance, resistivity, conductivity, factors affecting resistance, conventional current, electron flow, circuit symbols, and combinations of electric cells. It is easier and help you avoid common mistakes in the actual examination.
1. Electric potential at a point is defined as the:
Answer: A. Work done in bringing a unit positive charge from infinity to that point.
Electric potential is the amount of work required to bring a unit positive charge from infinity to a specific point in an electric field without changing its kinetic energy. It indicates the electrical potential energy possessed by a unit charge at that point. Electric potential is a scalar quantity and its SI unit is the volt (V). A greater electric potential enables charges to move through a conductor when a circuit is completed.
Quick Revision
- Electric potential is the work done per unit positive charge.
- It is a scalar quantity.
- SI unit: Volt (V).
- Electric potential is measured with respect to infinity.
Real-Life Example
A battery maintains a potential difference between its terminals, allowing electric current to flow when connected to an electrical device.
2. Which of the following expressions correctly represents electric current?
Answer: B. I = Q/t
Electric current is the rate at which electric charge flows through a conductor. It is calculated by dividing the amount of charge passing through a conductor by the time taken. The formula I = Q/t is the fundamental expression used to measure electric current, where I represents current, Q is electric charge, and t is time. The SI unit of electric current is the ampere (A).
Quick Revision
- Electric current is the rate of flow of electric charge.
- Formula: I = Q/t
- SI unit: Ampere (A).
- One ampere equals one coulomb of charge flowing per second.
Real-Life Example
When a mobile phone is charging, electric current flows through the charging cable into the battery.
3. Which of the following materials has the lowest electrical resistivity?
Answer: C. Copper
Electrical resistivity is the property of a material that opposes the flow of electric current. Copper has one of the lowest resistivity values among commonly used metals, allowing electricity to pass through it with very little resistance. Due to its excellent conductivity, durability, and flexibility, copper is widely used for electrical wiring in homes, industries, and electrical appliances.
Quick Revision
- Copper has very low electrical resistivity.
- Low resistivity means high electrical conductivity.
- Copper is widely used for electrical wiring.
- Good conductors allow electric current to flow easily.
Real-Life Example
The wires inside houses are generally made of copper because they transmit electricity efficiently with minimal energy loss.
4. The resistance of a conductor increases when its:
Answer: D. Length increases
The resistance of a conductor depends on its length, cross-sectional area, material, and temperature. When the length of a conductor increases, electrons travel a longer distance and collide more frequently with atoms inside the material. These collisions make it more difficult for current to flow, thereby increasing the resistance. This relationship is directly proportional and is represented by R ∝ L.
Quick Revision
- Resistance increases as the length of the conductor increases.
- Longer conductors oppose current more.
- Resistance decreases when the cross-sectional area increases.
- Material and temperature also affect resistance.
Real-Life Example
A long extension cable has more electrical resistance than a short cable made of the same material and thickness.
5. The SI unit of electrical resistivity is:
Answer: B. Ω·m
Electrical resistivity is a material property that indicates how strongly a substance resists the flow of electric current. Unlike resistance, resistivity depends only on the nature of the material and its temperature, not on its size or shape. The SI unit of resistivity is ohm-metre (Ω·m). Materials with low resistivity, such as copper and silver, are good conductors, whereas materials with high resistivity, such as rubber and glass, are good insulators.
Quick Revision
- SI unit of resistivity: Ohm-metre (Ω·m).
- Resistivity is a property of the material.
- Low resistivity indicates good conductivity.
- High resistivity materials are good insulators.
Real-Life Example
Copper wires are used in electrical circuits because their low resistivity allows electricity to flow efficiently, while plastic insulation prevents electric shock.
6. Which property of a material determines how easily electric current flows through it?
Answer: B. Conductivity
Conductivity is the property of a material that indicates how easily electric current can pass through it. Materials with high conductivity allow electrons to move freely and are called good conductors. Metals such as copper, silver, and aluminium have high conductivity, making them suitable for electrical wiring. Conductivity is the opposite of resistivity; as conductivity increases, resistivity decreases.
Quick Revision
- Conductivity measures how easily current flows.
- Good conductors have high conductivity.
- Copper and silver are excellent conductors.
- Conductivity is the opposite of resistivity.
Real-Life Example
Copper wires are used in household electrical circuits because their high conductivity allows electricity to flow efficiently.
7. Conventional current flows from:
Answer: A. Positive terminal to negative terminal
Conventional current is the assumed direction of electric current from the positive terminal to the negative terminal of a source. This convention was established before the discovery of electrons. In reality, electrons move from the negative terminal to the positive terminal, but circuit diagrams and electrical calculations continue to use the conventional current direction.
Quick Revision
- Conventional current flows from positive to negative.
- Electron flow is from negative to positive.
- Electrical circuit diagrams follow conventional current.
- Both directions describe the same electric circuit.
Real-Life Example
When drawing a circuit for a school experiment, the current direction is always shown from the positive terminal of the battery to the negative terminal.
8. Which of the following is a good conductor of electricity?
Answer: A. Silver
A good conductor is a material that allows electric current to pass through it with very little resistance. Silver has the highest electrical conductivity among all metals, making it the best conductor of electricity. However, because it is expensive, copper is more commonly used in electrical wiring for practical applications.
Quick Revision
- Silver is the best electrical conductor.
- Good conductors have low resistance.
- Copper is widely used because it is economical.
- Metals generally conduct electricity well.
Real-Life Example
Silver is used in high-quality electrical contacts and electronic components where maximum conductivity is required.
9. Resistance depends on all the following except:
Answer: D. Colour of the conductor
The resistance of a conductor depends on its length, cross-sectional area, material, and temperature. The colour of a conductor has no effect on the flow of electric current. Resistance changes only when one or more of the physical or material properties of the conductor change.
Quick Revision
- Resistance depends on length.
- Resistance depends on cross-sectional area.
- Resistance depends on the material and temperature.
- Colour does not affect electrical resistance.
Real-Life Example
A red electrical wire and a blue electrical wire made from the same material and having the same thickness will have the same electrical resistance.
10. A combination of two or more electric cells is called a:
Answer: C. Battery
A battery is a combination of two or more electric cells connected together to provide a greater amount of electrical energy. Cells may be connected in series to increase voltage or in parallel to increase the duration of current supply. Batteries are widely used in portable electronic devices, vehicles, emergency lighting systems, and power backup units.
Quick Revision
- A battery consists of two or more electric cells.
- Cells connected in series increase voltage.
- Cells connected in parallel increase operating time.
- Batteries store and supply electrical energy.
Real-Life Example
A car battery contains multiple cells connected together to supply sufficient electrical energy for starting the engine and operating electrical components.
11. The SI unit of electric current is:
Answer: A. Ampere
Electric current is the rate at which electric charge flows through a conductor. The SI unit of electric current is the ampere (A), named after the French physicist André-Marie Ampère. One ampere is defined as the flow of one coulomb of electric charge per second through a conductor. It is one of the seven base units in the International System of Units (SI).
Quick Revision
- SI unit of electric current: Ampere (A).
- Symbol of ampere: A.
- 1 ampere = 1 coulomb/second.
- Named after André-Marie Ampère.
Real-Life Example
A mobile phone charger supplies electric current measured in amperes to charge the battery safely and efficiently.
12. Ohm’s law states that:
Answer: B. Current is directly proportional to voltage at constant temperature.
Ohm’s Law states that the electric current flowing through a conductor is directly proportional to the potential difference across it, provided the temperature and other physical conditions remain constant. This relationship is expressed by the formula V = IR, where V is voltage, I is current, and R is resistance. Ohm’s Law helps in calculating unknown electrical quantities in electric circuits.
Quick Revision
- Ohm’s Law: V = IR.
- Current increases when voltage increases.
- Temperature must remain constant.
- Used to solve electrical circuit problems.
Real-Life Example
Electricians use Ohm’s Law while selecting suitable wires and electrical components for homes and industries.
13. Which instrument is used to measure electric current?
Answer: C. Ammeter
An ammeter is an electrical instrument used to measure the amount of electric current flowing through a circuit. It is always connected in series so that the entire current passes through it. An ammeter has very low resistance to avoid affecting the current in the circuit and provides readings in amperes.
Quick Revision
- Ammeter measures electric current.
- Connected in series with the circuit.
- Reading is measured in amperes.
- It has very low internal resistance.
Real-Life Example
During laboratory experiments, students use an ammeter to measure the current flowing through a resistor or bulb.
14. Which material is commonly used as the filament in an electric bulb?
Answer: D. Tungsten
Tungsten is used as the filament material in electric bulbs because it has a very high melting point and can withstand extremely high temperatures without melting. When electric current passes through the thin tungsten filament, it becomes white hot and emits light. Its strength and durability make it suitable for repeated heating and cooling.
Quick Revision
- Tungsten is used as a bulb filament.
- It has a very high melting point.
- It glows when heated by electric current.
- Suitable for high-temperature applications.
Real-Life Example
Traditional incandescent bulbs produce light because the tungsten filament becomes hot enough to glow brightly.
15. Which of the following offers the greatest resistance to the flow of electric current?
Answer: D. Rubber
Rubber is an electrical insulator with very high resistivity. It does not allow electric current to pass through easily, making it ideal for preventing electric shocks. Unlike metals such as copper and aluminium, rubber strongly opposes the movement of electrons and is therefore used as a protective insulating material.
Quick Revision
- Rubber is a good electrical insulator.
- It has very high electrical resistance.
- Insulators prevent the flow of current.
- Used for electrical safety.
Real-Life Example
The outer covering of electrical wires is made of rubber or PVC to protect people from electric shock while handling electrical appliances.
16. Which of the following devices converts electrical energy into mechanical energy?
Answer: C. Electric motor
An electric motor is a device that converts electrical energy into mechanical energy. It works on the principle that a current-carrying conductor placed in a magnetic field experiences a force, causing the motor to rotate. Electric motors are widely used in household appliances, industries, electric vehicles, and agricultural equipment because they efficiently produce mechanical motion.
Quick Revision
- An electric motor converts electrical energy into mechanical energy.
- It works using the force between electricity and magnetism.
- Used in many household and industrial machines.
- Electric motors require an electric current to operate.
Real-Life Example
Ceiling fans, washing machines, mixers, and water pumps all use electric motors to perform mechanical work.
17. Which of the following is the best conductor of electricity?
Answer: C. Silver
Silver is the best conductor of electricity because it has the highest electrical conductivity and the lowest resistivity among all metals. It allows electric current to flow with very little resistance. Although silver has excellent electrical properties, its high cost limits its use in household wiring, where copper is generally preferred.
Quick Revision
- Silver has the highest electrical conductivity.
- It offers very low resistance to current.
- Copper is commonly used as a practical alternative.
- Good conductors allow electrons to move easily.
Real-Life Example
Silver is used in high-quality electrical contacts, precision instruments, and electronic circuits where maximum conductivity is required.
18. The opposition offered by a conductor to the flow of electric current is called:
Answer: A. Resistance
Resistance is the property of a conductor that opposes the flow of electric current. It depends on the material, length, cross-sectional area, and temperature of the conductor. The SI unit of resistance is the ohm (Ω). According to Ohm’s Law, if the resistance increases while the voltage remains constant, the electric current decreases.
Quick Revision
- Resistance opposes the flow of electric current.
- SI unit: Ohm (Ω).
- Higher resistance results in lower current.
- Resistance depends on the conductor’s properties.
Real-Life Example
The heating coil inside an electric iron has high resistance, causing it to become hot when current passes through it.
19. Which of the following is a renewable source used to generate electricity?
Answer: A. Solar energy
Solar energy is a renewable source of energy because it is continuously supplied by the Sun and is naturally replenished. Solar panels use photovoltaic (PV) cells to convert sunlight directly into electrical energy without producing harmful air pollutants or greenhouse gases during operation. As a clean and sustainable energy source, solar power helps reduce dependence on fossil fuels and supports environmental conservation.
Quick Revision
- Solar energy is a renewable energy source.
- Solar panels convert sunlight into electricity.
- It is clean, sustainable, and environmentally friendly.
- Fossil fuels are non-renewable energy sources.
Real-Life Example
Many homes, schools, and government buildings install rooftop solar panels to generate electricity and reduce electricity bills.
20. The unit used to measure electric energy consumed in homes is:
Answer: B. Kilowatt-hour (kWh)
Electrical energy consumed in homes is measured in kilowatt-hours (kWh). One kilowatt-hour is the amount of energy used by a 1000-watt electrical appliance operating continuously for one hour. Electricity boards use the kilowatt-hour, commonly called one unit of electricity, to calculate electricity bills for consumers.
Quick Revision
- Household electrical energy is measured in kilowatt-hour (kWh).
- 1 kWh = Energy used by a 1000 W appliance in one hour.
- Electricity bills are based on the number of units consumed.
- kWh measures energy, not power.
Real-Life Example
If a 1000 W electric heater operates for one hour, it consumes 1 kWh (1 unit) of electrical energy, which appears on the monthly electricity bill.
Further Reading:
To build a stronger foundation in electricity, explore the official NCERT Science textbook, which explains concepts such as electric potential, potential difference, electric current, Ohm’s law, resistance, resistivity, electrical circuits, and circuit symbols in a simple and systematic manner. Revisiting these topics will complement your TNPSC Physics Electricity Test 3 preparation, improve your understanding of TNPSC General Science Electricity, and help you solve Physics MCQs for TNPSC with greater confidence.
Further Reading: Chapter 11 – Electricity
Great job on completing TNPSC Physics Electricity Test 3! Every quiz you finish adds a little more confidence and brings you one step closer to your TNPSC goal. Don’t stop with just one test—continue practicing the remaining electricity quizzes, learn from every explanation, and keep building your accuracy. Small, consistent practice today will make a big difference on exam day.