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❓ Important Questions
These questions cover the most important concepts,
reasoning, applications, diagrams and calculations
from the Electricity chapter.
Section A – Very Short Answer Questions
Q1
What is electric current?
Electric current is the rate of flow of electric charge
through a conductor.
Q2
What is the SI unit of electric current?
The SI unit is ampere (A).
Q3
State Ohm's law.
At constant temperature, potential difference across a
conductor is directly proportional to current through it:
V = IR.
Q4
What is resistance?
Resistance is the opposition offered by a conductor
to the flow of electric current.
Q5
What is the SI unit of resistance?
The SI unit of resistance is ohm (Ω).
Q6
What is resistivity?
Resistivity is a material property that characterises
how strongly a material opposes the flow of current.
Q7
What is the SI unit of electric power?
The SI unit of electric power is watt (W).
Q8
What is 1 kWh?
1 kWh is the energy consumed by a 1 kW appliance
operating for 1 hour.
Section B – Short Answer Questions
Q9
Why is an ammeter connected in series?
An ammeter measures the current flowing through a circuit,
so it must be connected so the circuit current passes
through the ammeter.
Q10
Why is a voltmeter connected in parallel?
A voltmeter measures the potential difference between two
points, so it is connected across the component.
Q11
What factors affect the resistance of a conductor?
Resistance depends on length, area of cross-section,
material and temperature.
Q12
Why does resistance increase when length of a wire increases?
A longer conductor provides a greater path through which
charge carriers must move, so resistance increases.
Q13
Why are household appliances connected in parallel?
Each appliance receives the supply potential difference
and can be switched on or off independently.
Q14
Why is a fuse used in an electrical circuit?
A fuse protects the circuit by melting and breaking the
circuit when excessive current flows.
Section C – Reasoning Questions
Q15
Why is the equivalent resistance in a parallel combination
less than the smallest resistor?
Parallel connection provides multiple paths for current,
thereby increasing the overall conductance and reducing
the equivalent resistance.
Q16
Why are electric heating elements made from materials
of relatively high resistivity?
A suitable high-resistance material can produce substantial
heat when current passes through it and can withstand
high operating temperatures.
Q17
Why does a bulb filament become hot when current passes through it?
Electrical energy is converted into heat due to the
resistance of the filament.
Q18
Why should an electric fuse be connected in series?
The fuse must carry the circuit current so that excessive
current causes it to heat and melt, disconnecting the circuit.
Section D – Long Answer Questions
Q19
Explain Ohm's law and describe the V-I graph for an ohmic conductor.
State Ohm's law, write V = IR and explain that for an ohmic
conductor at constant temperature, the V-I relationship is
linear and the graph passes through the origin.
Q20
Derive the equivalent resistance of resistors connected in series.
In series, current remains the same through each resistor.
The total potential difference is the sum of the individual
potential differences, giving:
R = R₁ + R₂ + R₃
Q21
Explain the equivalent resistance of resistors connected in parallel.
In parallel, the potential difference is the same across
each branch and total current is the sum of branch currents.
Therefore:
1/R = 1/R₁ + 1/R₂ + 1/R₃
Q22
Explain Joule's law of heating and give its applications.
The heat generated is given by
H = I²Rt.
Applications include electric heaters, irons, toasters,
kettles and fuse wires.
Section E – Application / Competency Questions
Q23
A 100 W bulb and a 1000 W heater are connected to the
same household supply. Which appliance consumes more
electrical energy in one hour?
The 1000 W heater consumes more energy because electrical
energy consumed is E = Pt.
Q24
Two wires are made of the same material and have the same
length, but one has twice the cross-sectional area.
Compare their resistances.
Since R = ρl/A, resistance is inversely proportional
to area. The wire with twice the area has half the resistance.
Q25
A circuit contains three resistors connected in parallel.
If one resistor is disconnected, will current through the
remaining branches necessarily stop?
No. In a parallel circuit, the remaining branches can continue
to carry current because they have separate conducting paths.
Q26
Why does a fuse protect an appliance during an overload?
Overload causes excessive current. The fuse wire heats up
and melts, opening the circuit and stopping the current.
Section F – Diagram-Based Questions
Q27
Draw a circuit diagram to verify Ohm's law.
Include battery, key, rheostat, ammeter, resistor and
voltmeter. Ammeter is in series and voltmeter is connected
in parallel with the resistor.
Q28
Draw a series combination of three resistors.
Show the three resistors connected end-to-end in a single
current path.
Q29
Draw a parallel combination of three resistors.
Show three separate branches connected between the same
two points of the circuit.
Q30
Draw a household circuit showing appliances connected in parallel.
Show separate branches for different appliances with
appropriate switches and protective devices.
⚡ Final Exam Focus
-
Ohm's law and V-I graph
-
Resistance and resistivity
-
Series and parallel combinations
-
Joule's law of heating
-
Electrical power and energy
-
kWh and unit conversion
-
Household circuits and fuse