What does the term “electrical grounding” refer to?
A Reducing voltage
B Connecting a circuit to the Earth
C Increasing current flow
D Stopping electric shocks
Grounding provides a safe path for excess current to flow into the Earth, protecting people and equipment from electric shocks.
Which law governs the total voltage around a closed loop in a circuit?
A Kirchhoff’s Voltage Law
B Ohm’s Law
C Coulomb’s Law
D Ampere’s Law
Kirchhoff’s Voltage Law states that the sum of all voltages around a closed loop is zero, accounting for voltage rises and drops.
What is the main reason for using insulation on electrical wires?
A To reduce voltage
B To prevent current flow
C To avoid electric shocks
D To improve conductivity
Insulation covers the conductor to prevent accidental contact, reducing the risk of electric shocks and short circuits.
What is the primary function of a capacitor in an AC circuit?
A To store charge
B To increase resistance
C To decrease voltage
D To block DC current
A capacitor allows AC signals to pass while blocking DC due to its impedance. It also stores charge temporarily.
The resistance of a conductor depends on:
A Length and material
B Cross-sectional area
C Temperature
D All of the above
Resistance depends on a conductor’s length, cross-sectional area, material resistivity, and temperature.
What is the unit of electrical energy?
A Joule
B Watt
C Volt
D Ampere
Electrical energy is measured in joules (J). One joule is the energy transferred when one watt of power is used for one second.
Which of the following is a non-ohmic conductor?
A Copper wire
B Filament of a bulb
C Aluminum wire
D Gold wire
Non-ohmic conductors do not follow Ohm’s Law. The resistance of a bulb filament changes with temperature, making it non-ohmic.
What is the function of a diode?
A To amplify current
B To allow current in one direction only
C To store electrical energy
D To reduce resistance
A diode is a semiconductor device that permits current flow in one direction and blocks it in the opposite direction.
Which of the following is a passive electrical component?
A Transistor
B Resistor
C Thyristor
D Diode
A passive component, like a resistor, does not generate power but dissipates or stores it.
What does an electric circuit require to work?
A A power source
B Conductors
C A load
D All of the above
An electric circuit must include a power source (e.g., battery), conductors (e.g., wires), and a load (e.g., bulb) to function properly.
Which quantity is inversely proportional to resistance in a conductor?
A Voltage
B Conductance
C Current
D Power
Conductance (G) is the reciprocal of resistance (R): G = 1/R. It measures how easily current flows through a material.
What is the unit of electrical capacitance?
A Henry
B Coulomb
C Farad
D Tesla
Capacitance is measured in farads (F). One farad is the capacitance when one coulomb of charge causes a potential difference of one volt.
In an AC circuit, what is the phase difference between voltage and current in a purely capacitive circuit?
A 0°
B 90°
C 180°
D 270°
In a purely capacitive circuit, the current leads the voltage by 90° due to the energy exchange between the capacitor and the source.
Which of the following electrical quantities remains constant in a parallel circuit?
A Voltage
B Current
C Resistance
D Power
In a parallel circuit, the voltage across each branch is the same, regardless of the resistance or current in the branch.
What type of material is used as an insulator in electrical appliances?
A Copper
B Plastic
C Aluminum
D Brass
Plastic is a good insulator due to its high electrical resistivity, preventing the flow of electric current and protecting users from shocks.
Which of the following is a safety device used to prevent electric shock?
A Resistor
B Circuit Breaker
C Capacitor
D Transformer
A circuit breaker automatically interrupts the flow of current when it exceeds a safe level, preventing electric shocks and protecting the circuit.
What is the purpose of a neutral wire in a domestic electrical circuit?
A To carry current to the appliance
B To provide a return path for current
C To increase voltage
D To reduce resistance
The neutral wire completes the circuit by providing a return path for the current to the power source, ensuring circuit functionality.
What happens to the magnetic field around a conductor when current flows through it?
A It disappears
C It is created around the conductor
B It remains unchanged
D It reverses direction
When current flows through a conductor, a magnetic field is generated around it. The direction of the field is determined by the right-hand rule.
Which component stores energy in a magnetic field?
A Capacitor
B Inductor
C Resistor
D Diode
An inductor stores energy in its magnetic field when current flows through it, and releases the energy when the current decreases.
What type of current is used in household electrical systems?
A Direct Current (DC)
B Alternating Current (AC)
C Pulsating Current
D Static Current
Household electrical systems use AC because it can be efficiently transmitted over long distances and easily transformed to different voltage levels.
Which of the following defines one joule of energy?
A The work done by a current of one ampere in one second
B The work done when a force of one newton moves an object by one meter
C The energy required to move one coulomb of charge through one volt
D All of the above
One joule is a unit of energy equivalent to one newton-meter or one coulomb-volt. It also equals the work done by a one-ampere current in one second.
Which electrical quantity is measured in ohms?
A Current
B Voltage
C Resistance
D Capacitance
Resistance, which opposes the flow of current in a circuit, is measured in ohms (Ω).
What is the primary function of a relay in an electrical circuit?
A To store energy
B To measure current
C To switch a circuit on or off remotely
D To reduce voltage
A relay is an electromechanical device that uses a small control signal to operate a larger load circuit, providing isolation and control.
What is the frequency of the standard AC supply in most countries?
A 25 Hz
B 50 Hz
C 75 Hz
D 100 Hz
In most countries, the AC supply frequency is standardized at 50 Hz. In the U.S. and some other countries, it is 60 Hz.
What happens to the power in a circuit if the voltage is doubled while the resistance remains constant?
A It is halved
B It remains the same
C It doubles
D It quadruples
Power (P) in a resistive circuit is given by P = V²/R. If the voltage (V) doubles, the power increases by a factor of four.
What is the main purpose of an electrical grounding system?
A To save energy
B To protect against voltage surges
C To prevent electric shock
D Both B and C
Grounding protects against voltage surges and ensures excess current flows safely to the Earth, preventing electric shocks.
Which device converts mechanical energy into electrical energy?
A Motor
B Generator
C Transformer
D Battery
A generator uses electromagnetic induction to convert mechanical energy into electrical energy.
What type of wave does AC produce?
A Square wave
B Sine wave
C Triangular wave
D Pulsed wave
Alternating current (AC) typically produces a sinusoidal waveform, which repeats periodically.
What is the effect of increasing the length of a wire on its resistance?
A Decreases resistance
B Increases resistance
C No effect
D Resistance becomes zero
Resistance is directly proportional to the length of the wire: R = ρL/A, where L is the length and ρ is the resistivity.
Which device is used to measure high voltages?
A Multimeter
B Voltmeter
C Megger
D Oscilloscope
A megger is specifically designed to measure high voltages and insulation resistance in electrical systems.
Which component opposes the change in current in a circuit?
A Resistor
B Capacitor
C Inductor
D Diode
An inductor opposes changes in current through it by generating a counter-electromotive force (EMF) according to Lenz’s Law.
What is the relationship between voltage and current in a purely resistive circuit?
A Voltage leads current by 90°
B Voltage lags current by 90°
C Voltage and current are in phase
D Voltage and current are out of phase
In a resistive circuit, voltage and current change simultaneously because resistance does not cause phase shifts.
Which of the following devices uses the principle of electromagnetic induction?
A Transformer
B Capacitor
C Resistor
D Battery
A transformer operates on the principle of electromagnetic induction to transfer electrical energy between two coils by mutual induction.
What is the unit of inductance?
A Farad
B Ohm
C Henry
D Watt
Inductance is measured in henries (H). One henry is the inductance when a current change of one ampere per second induces an EMF of one volt.
In a series RLC circuit, at resonance, the impedance is:
A Maximum
B Minimum
C Zero
D Infinite
At resonance, the inductive reactance and capacitive reactance cancel each other, leaving only the resistance, which is the minimum impedance in the circuit.
Which electrical symbol represents a resistor in a circuit diagram?
A A zigzag line
B A straight line
C A circle with a cross
D A rectangle
A resistor is represented by a zigzag line in circuit diagrams, indicating its role in resisting current flow.
Which of the following determines the polarity of an induced voltage in a conductor?
A Coulomb’s Law
B Faraday’s Law
C Lenz’s Law
D Ohm’s Law
Lenz’s Law states that the direction of induced EMF opposes the change in magnetic flux that caused it, determining polarity.
Which safety device detects and interrupts leakage currents to prevent electric shocks?
A Fuse
B Circuit Breaker
C Residual Current Device (RCD)
D Transformer
An RCD detects leakage currents caused by faults and quickly disconnects the circuit to protect users from electric shocks.
What is the main purpose of a step-down transformer?
A To increase current
B To reduce voltage
C To decrease power
D To improve resistance
A step-down transformer reduces the voltage level while increasing the current proportionally, maintaining the same power.
What is the total capacitance when capacitors are connected in series?
A Equal to the sum of individual capacitances
B Less than the smallest capacitance
C Equal to the largest capacitance
D Equal to the product of capacitances
In a series connection, the total capacitance is calculated using: \( 1/C_{\text{total}} = 1/C_1 + 1/C_2 + … \), resulting in a value less than the smallest individual capacitance.
What is the purpose of using a rheostat in a circuit?
A To measure voltage
B To vary resistance
C To amplify current
D To convert AC to DC
A rheostat is a variable resistor used to adjust current flow by changing the resistance in the circuit.
What is the main difference between AC and DC?
A AC flows in one direction, while DC reverses direction
B AC reverses direction periodically, while DC flows in one direction
C AC has higher voltage than DC
D DC is safer than AC
Alternating current (AC) changes direction periodically, whereas direct current (DC) flows steadily in a single direction.
Which of the following appliances typically uses a DC motor?
A Ceiling fan
B Vacuum cleaner
C Electric car
D Refrigerator
Electric cars use DC motors for their high efficiency and control over speed and torque.
What is the standard voltage level for residential wiring in most countries?
A 120V or 230V
B 12V or 24V
C 400V or 415V
D 600V or 1000V
Most residential systems use either 120V (e.g., USA) or 230V (e.g., Europe and India) depending on the country’s electrical standards.
Which component converts AC to DC in an electrical circuit?
A Diode
B Transformer
C Resistor
D Capacitor
A diode acts as a rectifier, allowing current to flow in one direction only, thus converting AC to DC.
Which factor affects the resistance of a conductor?
A Length
B Cross-sectional area
C Material
D All of the above
Resistance depends on the length, cross-sectional area, and material of the conductor, as described by the formula \( R = \rho \frac{L}{A} \), where \( \rho \) is resistivity.
What is the purpose of a multimeter?
A To measure current only
B To measure resistance only
C To measure multiple quantities like voltage, current, and resistance
D To measure temperature
A multimeter is a versatile device used to measure voltage, current, resistance, and sometimes other parameters.
What does the term “short circuit” mean?
A High resistance in the circuit
B A direct connection between two points of different potentials
C No current in the circuit
D A completely open circuit
A short circuit occurs when two points with different potentials are connected directly, leading to a high current flow and potential damage.
What is the efficiency of an ideal transformer?
A 0%
B 50%
C 100%
D Infinite
An ideal transformer has no losses, so all the input power is transferred to the output, giving it 100% efficiency.
Which device is used to detect the presence of electric fields?
A Voltmeter
B Galvanometer
C Electroscope
D Ammeter
An electroscope is used to detect the presence of electric charges or electric fields by observing the deflection of its metal leaves.