Electricity Practice Questions
20 free Electricity practice questions for the Static GK. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which of the following defines the SI unit of electric current, the Ampere?
- A One joule of energy per second
- B One volt per second
- C One ohm per volt
- D One coulomb per second
Correct answer: One coulomb per second
Electric current is defined as the rate of flow of electric charge. One Ampere represents the flow of one Coulomb of charge passing through a cross-section of a conductor in one second.
According to Ohm's Law, what happens to the current flowing through a conductor if the resistance is doubled while the potential difference remains constant?
- A The current is doubled.
- B The current remains the same.
- C The current is reduced to half.
- D The current becomes four times greater.
Correct answer: The current is reduced to half.
Ohm's Law states that V = IR, which can be rearranged to I = V/R. If the resistance R is doubled (2R) and voltage V is constant, the current I becomes half of its original value.
What is the equivalent resistance of two resistors, 6 Ω and 3 Ω, connected in parallel?
- A 2 Ω
- B 9 Ω
- C 4.5 Ω
- D 18 Ω
Correct answer: 2 Ω
For resistors in parallel, the reciprocals add: 1/Rt = 1/6 + 1/3 = 1/6 + 2/6 = 3/6 = 1/2. Taking the reciprocal gives Rt = 2 Ω, which is always less than the smaller of the two resistances.
Which material is typically used for the filament of an incandescent light bulb due to its high melting point?
- A Copper
- B Nichrome
- C Tungsten
- D Aluminum
Correct answer: Tungsten
Tungsten has an extremely high melting point (3422°C), which allows it to glow white-hot without melting. This property is essential for the durability of incandescent filaments.
The rate at which electrical energy is dissipated as heat in a resistor is given by which formula?
- A P = I²R
- B P = V/I
- C P = VR
- D P = I/V²
Correct answer: P = I²R
Electrical power P is the product of voltage and current (VI). By substituting V = IR (Ohm's Law), we get P = (IR)I, which simplifies to P = I²R, often called Joule heating.
What is the function of a fuse in an electric circuit?
- A To increase the voltage of the circuit.
- B To store electrical charge.
- C To break the circuit if the current exceeds a safe limit.
- D To convert alternating current into direct current for appliances.
Correct answer: To break the circuit if the current exceeds a safe limit.
A fuse contains a thin wire with a low melting point that melts when excessive current flows through it. This breaks the circuit and protects electrical appliances from damage and fire hazards.
If three identical bulbs are connected in series and one bulb burns out, what happens to the other two bulbs?
- A They stay lit with the same brightness.
- B They become brighter.
- C They become dimmer.
- D They go out completely.
Correct answer: They go out completely.
In a series circuit, there is only one path for the current to follow. If one component fails, the circuit is broken and current stops flowing through all other components.
What is the commercial unit of electrical energy often used in utility bills?
- A British thermal unit
- B Watt
- C Ampere-hour
- D Kilowatt-hour
Correct answer: Kilowatt-hour
The kilowatt-hour (kWh) represents the energy consumed by a 1000-watt appliance running for one hour. One kWh is equivalent to 3.6 million Joules.
How should an ammeter be connected in a circuit to measure the current through a resistor?
- A In series with the resistor
- B In parallel with the resistor
- C Across the battery
- D Between the ground and the resistor
Correct answer: In series with the resistor
An ammeter must be connected in series so that the entire current of the branch passes through it. Ammeters are designed with very low resistance to avoid affecting the circuit's total current.
The resistivity of a wire depends primarily on which of the following?
- A The length of the wire
- B The cross-sectional area and thickness of the wire
- C The shape of the wire
- D The nature of the material and temperature
Correct answer: The nature of the material and temperature
While resistance depends on dimensions (length and area), resistivity is an intrinsic property of the material. It varies only with the type of material and its temperature.
Which of the following describes the behavior of a superconductor?
- A It has very high electrical resistance at all temperatures.
- B It has zero electrical resistance below a critical temperature.
- C It allows electric current to flow in only one direction.
- D It converts heat directly into electricity with perfect efficiency.
Correct answer: It has zero electrical resistance below a critical temperature.
Superconductivity is a phenomenon where certain materials exhibit exactly zero electrical resistance when cooled below a specific transition temperature. This allows current to flow indefinitely without energy loss.
Which law states that the total charge arriving at a junction each second equals the total charge leaving it?
- A Ohm's Law
- B Kirchhoff's Current Law
- C Coulomb's Law of Electrostatics
- D Faraday's Law of Induction
Correct answer: Kirchhoff's Current Law
Kirchhoff's Current Law (KCL) is based on the principle of conservation of electric charge. Charge cannot be created or destroyed at a junction, so the net flow must be zero.
What is the direction of 'conventional current' in an external circuit?
- A From the negative terminal to the positive terminal
- B In the same direction as the flow of electrons in the wire
- C From the positive terminal to the negative terminal
- D It reverses direction many times per second
Correct answer: From the positive terminal to the negative terminal
Conventional current was defined before the discovery of electrons as the flow of positive charge. Consequently, it is described as moving from the positive terminal to the negative terminal, opposite to the actual electron flow.
A 100 W bulb and a 60 W bulb are connected in series to a power source. Which bulb will glow brighter?
- A The 100 W bulb
- B The 60 W bulb
- C Both equally
- D Neither will glow
Correct answer: The 60 W bulb
In series, both bulbs share the same current. Since P = I²R and the 60 W bulb has a higher resistance than the 100 W bulb (assuming the same rated voltage), it will dissipate more power and glow brighter in a series configuration.
What happens to the resistance of a semiconductor like Silicon as its temperature increases?
- A It increases.
- B It decreases.
- C It remains constant.
- D It becomes zero.
Correct answer: It decreases.
Unlike metals, semiconductors have a negative temperature coefficient of resistance. As temperature rises, more electrons gain enough energy to jump into the conduction band, increasing conductivity and decreasing resistance.
The work done in moving a unit positive charge from one point to another in an electric circuit is known as:
- A Electric Current
- B Electric Power
- C Potential Difference
- D Electrical Resistance
Correct answer: Potential Difference
Potential difference (or voltage) is defined as the work done per unit charge. It provides the 'pressure' or 'push' needed to move charges through a conductor.
Which device is used to change the voltage of an alternating current (AC) without changing its frequency?
- A Generator
- B Electric motor
- C Transformer
- D Rectifier
Correct answer: Transformer
A transformer uses electromagnetic induction between two coils to step up or step down AC voltage levels. It is highly efficient and fundamental to modern power distribution systems.
Which of the following is an example of an 'Ohmic' conductor?
- A Diode
- B Transistor
- C Copper wire
- D Filament lamp
Correct answer: Copper wire
An Ohmic conductor is one that strictly follows Ohm's Law, where current is directly proportional to voltage (resulting in a linear graph). Metals like copper behave this way at constant temperatures.
In a domestic circuit, why are all appliances connected in parallel?
- A To ensure that every appliance carries exactly the same current.
- B To ensure they all receive the same voltage and work independently.
- C To lower the total resistance and reduce the electricity bill.
- D To stop the main fuse from blowing whenever a device is switched on.
Correct answer: To ensure they all receive the same voltage and work independently.
Parallel connections allow each appliance to receive the full mains voltage (e.g., 230V or 120V). It also ensures that turning off one appliance does not interrupt the circuit for others.
What color is the 'earth wire' (ground wire) typically coded in modern international standards?
- A Solid red
- B Solid black
- C Green and yellow
- D Light blue with a white stripe
Correct answer: Green and yellow
Modern wiring standards use green-and-yellow striped insulation for the earth wire. This wire provides a low-resistance path to the ground so that a fault current trips the protective device instead of passing through a person.