Electricity

What is the SI unit of electric current?
a) Volt
b) Ohm
c) Ampere
d) Watt
✅ c) Ampere
Explanation: Ampere is the unit for measuring electric current flow.

What device measures electric current?
a) Voltmeter
b) Ammeter
c) Ohmmeter
d) Galvanometer
✅ b) Ammeter
Explanation: Ammeters are used to measure current and are connected in series.

Which instrument measures voltage?
a) Voltmeter
b) Ammeter
c) Thermometer
d) Hydrometer
✅ a) Voltmeter
Explanation: Voltmeters are connected in parallel to measure potential difference.

What does Ohm's law state?
a) I = V + R
b) V = I/R
c) V = I × R
d) R = V – I
✅ c) V = I × R
Explanation: Voltage across a conductor is proportional to current through it.

The resistance of a conductor depends on:
a) Length
b) Area of cross-section
c) Material
d) All of the above
✅ d) All of the above
Explanation: Resistance increases with length, decreases with cross-sectional area.

SI unit of resistance is:
a) Ampere
b) Volt
c) Ohm
d) Joule
✅ c) Ohm
Explanation: Resistance is measured in ohms (Ω).

What is the SI unit of electric power?
a) Watt
b) Joule
c) Volt
d) Ampere
✅ a) Watt
Explanation: 1 watt = 1 joule/second.

Electric energy is commonly measured in:
a) Joule
b) Watt
c) Watt-hour
d) Kilowatt-hour
✅ d) Kilowatt-hour
Explanation: 1 kWh = 1000 watts used for 1 hour = 3.6 × 10⁶ joules.

What is the function of a fuse in an electric circuit?
a) Increase voltage
b) Reduce current
c) Prevent overcurrent
d) Store energy
✅ c) Prevent overcurrent
Explanation: Fuse melts when current exceeds safe limit, breaking the circuit.

Which type of current is supplied to homes in India?
a) Direct Current (DC)
b) Alternating Current (AC)
c) Pulsed Current
d) Rotating Current
✅ b) Alternating Current (AC)
Explanation: AC is supplied at 220 V and 50 Hz in Indian households.

A closed circuit allows:
a) No current
b) Leakage
c) Continuous current
d) Infinite resistance
✅ c) Continuous current
Explanation: A closed loop allows current to flow without interruption.

Current in a circuit flows from:
a) Negative to positive terminal
b) Positive to negative terminal
c) Ground to live
d) Earth to circuit
✅ b) Positive to negative terminal
Explanation: Conventional current flows from positive to negative.

Who discovered the concept of electric current?
a) Newton
b) Ohm
c) Volta
d) André-Marie Ampère
✅ d) André-Marie Ampère
Explanation: The unit Ampere is named after him.

A 100 W bulb used for 10 hours consumes:
a) 0.1 kWh
b) 1 kWh
c) 10 kWh
d) 100 kWh
✅ b) 1 kWh
Explanation: Power × time = 100 × 10 = 1000 Wh = 1 kWh.

Which metal is used in household wiring?
a) Iron
b) Copper
c) Silver
d) Aluminum
✅ b) Copper
Explanation: Copper is a good conductor and cost-effective.

What is an insulator?
a) Allows easy flow of current
b) Prevents flow of current
c) Converts current to light
d) Transfers heat
✅ b) Prevents flow of current
Explanation: Materials like rubber, glass block current flow.

Which device converts chemical energy into electrical energy?
a) Generator
b) Transformer
c) Battery
d) Motor
✅ c) Battery
Explanation: Batteries use chemical reactions to produce electric current.

In a series circuit:
a) Voltage is divided
b) Current is constant
c) Resistance is zero
d) Current is divided
✅ b) Current is constant
Explanation: Same current flows through all components in series.

In a parallel circuit:
a) Voltage is same
b) Current is same
c) Resistance is minimum
d) Both a and c
✅ d) Both a and c
Explanation: In parallel, all branches get equal voltage; equivalent resistance decreases.

The resistance of a wire increases with:
a) Decreasing length
b) Increasing thickness
c) Increasing length
d) Lower temperature
✅ c) Increasing length
Explanation: Resistance ∝ length.

Electric current is measured in terms of:
a) Flow of atoms
b) Flow of heat
c) Flow of electrons
d) Flow of waves
✅ c) Flow of electrons
Explanation: Current is movement of electrons through a conductor.

The heating effect of electric current depends on:
a) Current
b) Resistance
c) Time
d) All of the above
✅ d) All of the above
Explanation: H = I²Rt (Joule’s Law of heating).

Which law explains heating due to current?
a) Newton’s law
b) Joule’s law
c) Ohm’s law
d) Faraday’s law
✅ b) Joule’s law
Explanation: Heat = I²Rt.

A diode allows current to flow in:
a) Two directions
b) No direction
c) One direction
d) Random direction
✅ c) One direction
Explanation: Diodes conduct current in only one direction.

Which material is commonly used for heating coils?
a) Iron
b) Nichrome
c) Copper
d) Zinc
✅ b) Nichrome
Explanation: It has high resistance and doesn't oxidize easily.

The flow of charges in one direction is called:
a) AC
b) DC
c) Static
d) Capacitive
✅ b) DC
Explanation: DC flows in one direction, unlike AC which reverses.

Voltage is measured in:
a) Ampere
b) Watt
c) Ohm
d) Volt
✅ d) Volt
Explanation: 1 Volt = 1 Joule/Coulomb.

What is the role of a resistor?
a) Increases current
b) Reduces resistance
c) Controls current
d) Generates voltage
✅ c) Controls current
Explanation: Resistors limit the flow of current in circuits.

Lightning is a natural form of:
a) Solar energy
b) Static electricity
c) Magnetic field
d) Kinetic energy
✅ b) Static electricity
Explanation: Accumulated charges in clouds cause lightning.

What is short circuit?
a) Long path
b) Open circuit
c) Direct connection of positive and negative
d) Resistance increase
✅ c) Direct connection of positive and negative
Explanation: Causes sudden rise in current, may result in fire.

A switch is used to:
a) Store electricity
b) Break or complete a circuit
c) Increase resistance
d) Change voltage
✅ b) Break or complete a circuit
Explanation: Switches control the flow of electricity.

Power of an appliance is calculated as:
a) P = I × R
b) P = V/I
c) P = V × I
d) P = R/I
✅ c) P = V × I
Explanation: Power equals voltage × current.

Which energy conversion takes place in an electric fan?
a) Electrical → Heat
b) Electrical → Mechanical
c) Mechanical → Electrical
d) Electrical → Light
✅ b) Electrical → Mechanical
Explanation: Motor converts electric energy into blade motion.

Electric wires are coated with:
a) Paper
b) Rubber
c) Metal
d) Plastic
✅ d) Plastic
Explanation: Plastic acts as an insulator to prevent shocks.

Conductors have:
a) High resistance
b) No resistance
c) Low resistance
d) Negative charge
✅ c) Low resistance
Explanation: They allow current to pass easily.

A device that stores electrical energy is:
a) Capacitor
b) Resistor
c) Generator
d) Transformer
✅ a) Capacitor
Explanation: Capacitors store and discharge electric charge.

Electrical energy is measured in:
a) Volts
b) Watts
c) kWh
d) Ohms
✅ c) kWh
Explanation: Unit used in electricity bills.

An electric motor converts:
a) Chemical → Electrical
b) Electrical → Mechanical
c) Mechanical → Electrical
d) Electrical → Thermal
✅ b) Electrical → Mechanical
Explanation: Used in fans, mixers, etc.

Static electricity is caused by:
a) Flowing current
b) Battery
c) Accumulation of charge
d) Electromagnets
✅ c) Accumulation of charge
Explanation: Stationary charges build up due to friction.

Which one is a poor conductor?
a) Copper
b) Silver
c) Glass
d) Aluminium
✅ c) Glass
Explanation: Insulator; does not allow free flow of electrons.

Who discovered electricity generation using magnetism?
a) Volta
b) Faraday
c) Ampere
d) Newton
✅ b) Faraday
Explanation: He discovered electromagnetic induction.

What is the standard voltage in Indian households?
a) 110 V
b) 220 V
c) 440 V
d) 12 V
✅ b) 220 V
Explanation: India uses 220V, 50 Hz AC supply.

What is the frequency of AC in India?
a) 50 Hz
b) 60 Hz
c) 100 Hz
d) 25 Hz
✅ a) 50 Hz
Explanation: AC alternates 50 times per second in India.

Which metal is best conductor of electricity?
a) Copper
b) Gold
c) Silver
d) Aluminium
✅ c) Silver
Explanation: Silver is best but expensive, so copper is preferred.

What is the use of earthing?
a) Reduce electricity bills
b) Stabilize voltage
c) Prevent shock
d) Store energy
✅ c) Prevent shock
Explanation: Earthing diverts excess charge to the ground.

LED stands for:
a) Light Efficient Display
b) Light Emitting Diode
c) Light Energy Device
d) Laser Emitting Diode
✅ b) Light Emitting Diode
Explanation: Emits light when current flows through it.

A transformer is used to:
a) Convert DC to AC
b) Store energy
c) Increase or decrease voltage
d) Generate current
✅ c) Increase or decrease voltage
Explanation: Works on AC using electromagnetic induction.

Which type of current flows only in one direction?
a) Alternating current
b) Direct current
c) Static
d) Magnetic
✅ b) Direct current
Explanation: DC flows from one terminal to another.

What causes electric shock?
a) Light
b) Current through the body
c) Voltage loss
d) Low frequency
✅ b) Current through the body
Explanation: Current disrupts normal body functions.

Fuse wire is made of:
a) Iron
b) Tin-lead alloy
c) Copper
d) Zinc
✅ b) Tin-lead alloy
Explanation: Has low melting point, breaks circuit in case of overload.