CBSE Class 10 Science • Circuits and Electrical Energy
Electricity Class 10 Worksheet with Answers
How does current depend on voltage and resistance? Why do appliances use parallel connections, and how is electrical energy consumption calculated? Use the Electricity Class 10 worksheet with answers to revise electric current, potential difference, Ohm’s law, resistor combinations, heating effect and electric power.
Electricity questions combine definitions, circuit diagrams, graphs and numerical calculations. Understanding the relationships between quantities makes it easier to select the correct formula and explain the result. Attempt the worksheet independently, then check the answers to identify errors in concepts, units or calculations.
The Electricity Class 10 short notes and worked examples below support revision before a chapter test. Practise writing the given values, selecting a formula and showing each calculation clearly instead of jumping directly to an answer.
Electricity Class 10 Summary
Electric Current and Charge
Electric current is the rate of flow of electric charge through a cross-section. Its SI unit is the ampere. A current of one ampere means that one coulomb of charge passes through a cross-section in one second.
Current formula: I = Q/t
I = current in amperes.
Q = charge in coulombs.
t = time in seconds.
Unit relationship: 1 A = 1 C/s.
Conventional current follows the direction in which positive charge would move. In a metallic conductor, electrons drift in the opposite direction to conventional current.
Potential Difference
Potential difference expresses the energy transferred per unit charge between two points. Its SI unit is the volt. A potential difference of one volt corresponds to one joule of energy transferred per coulomb of charge.
Potential difference: V = W/Q
Unit relationship: 1 V = 1 J/C.
Ohm’s Law Class 10
Ohm’s law states that the current through an ohmic conductor is directly proportional to the potential difference across it when temperature and other physical conditions remain constant. The relationship is written as V = IR.
Check the Axes Before Finding Resistance
On a graph with V on the vertical axis and I on the horizontal axis, the slope gives resistance: R = ΔV/ΔI. If the axes are reversed, the slope gives 1/R.
Resistance and Resistivity
Resistance describes how a component opposes current. For a uniform wire, resistance depends on its length, cross-sectional area, material and temperature. Resistivity is a property of the material at a specified temperature.
Resistance of a uniform wire: R = ρL/A
R = resistance in ohms.
ρ = resistivity in ohm metres.
L = length in metres.
A = cross-sectional area in square metres.
- Doubling length doubles resistance if area, material and temperature remain unchanged.
- Doubling cross-sectional area halves resistance under the same conditions.
- Changing a wire’s dimensions does not change its material’s resistivity at the same temperature.
- For a circular wire, cross-sectional area depends on the square of its radius.
Resistors in Series and Parallel
| Feature | Series | Parallel |
|---|---|---|
| Arrangement | Components lie along a single current path. | Components form branches between the same two points. |
| Current | The same current passes through each resistor. | Total current equals the sum of branch currents. |
| Potential difference | Total voltage equals the sum of individual voltage drops. | The same voltage acts across each branch. |
| Equivalent resistance | Rₛ = R₁ + R₂ + R₃ | 1/Rₚ = 1/R₁ + 1/R₂ + 1/R₃ |
| Useful check | For positive resistances, the total exceeds each individual resistance. | For multiple positive resistances, the total is smaller than the smallest branch resistance. |
Appliances are connected in parallel so that each receives the supply voltage and can be controlled independently. Switching off one branch does not normally interrupt the others.
Heating Effect of Electric Current
Current through a resistor transfers electrical energy into thermal energy. Joule’s law of heating gives H = I²Rt when current and resistance are constant during the time considered. Electric heaters, irons and toasters use this effect.
State What Remains Constant
At fixed current, heating power I²R increases with resistance. At fixed voltage, heating power V²/R decreases as resistance increases. Always identify the condition before comparing heat production.
Electric Power and Electrical Energy
Power is the rate of energy transfer. A watt means one joule per second. Electrical energy depends on both appliance power and operating time.
| Quantity | Formula | Unit |
|---|---|---|
| Current | I = Q/t | Ampere, A |
| Potential difference | V = W/Q | Volt, V |
| Resistance | R = V/I | Ohm, Ω |
| Resistivity | ρ = RA/L | Ohm metre, Ω m |
| Power | P = VI | Watt, W |
| Power in a resistor | P = I²R = V²/R | Watt, W |
| Electrical energy | E = Pt | Joule or kilowatt-hour |
| Joule heating | H = I²Rt | Joule, J |
One Unit of Electrical Energy
1 kWh = 1000 W × 3600 s
1 kWh = 3.6 × 10⁶ J
One commercial unit of electrical energy equals one kilowatt-hour. A kilowatt-hour measures energy, while a kilowatt measures power.
Electricity Class 10 Numericals with Solutions
Example 1: Calculate Current
A charge of 120 C passes through a conductor in 2 minutes. Find the current.
Q = 120 C
t = 2 × 60 s
t = 120 s
I = Q/t
I = 120/120
I = 1 A
Answer: The current is 1 A.
Example 2: Series and Parallel Resistance
Find the equivalent resistance of 6 Ω and 3 Ω resistors connected first in series and then in parallel.
Series:
Rₛ = R₁ + R₂
Rₛ = 6 + 3
Rₛ = 9 Ω
Parallel:
1/Rₚ = 1/6 + 1/3
1/Rₚ = 1/6 + 2/6
1/Rₚ = 3/6
Rₚ = 2 Ω
Answer: 9 Ω in series and 2 Ω in parallel.
Example 3: Heating Effect
A current of 2 A passes through a 5 Ω resistor for 3 minutes. Calculate the heat produced.
I = 2 A
R = 5 Ω
t = 3 × 60 s
t = 180 s
H = I²Rt
H = 2² × 5 × 180
H = 3600 J
Answer: The heat produced is 3600 J.
Example 4: Energy Consumption
A 1000 W heater operates for 2 hours daily for 30 days. Calculate its energy consumption.
P = 1000 W
P = 1 kW
t = 2 × 30 h
t = 60 h
E = Pt
E = 1 × 60
E = 60 kWh
Answer: The heater uses 60 units of electrical energy, assuming it operates continuously at its rated power.
Circuit Diagrams and Ohm’s Law Experiment
Practise drawing a cell or battery, switch, resistor, rheostat, ammeter and voltmeter using standard symbols. Connect the ammeter in series with the component and the voltmeter in parallel across it.
- Label the instruments and resistor clearly.
- Use the rheostat to obtain different current readings.
- Record corresponding voltage and current values.
- Plot the graph with labelled axes and units.
- For an ohmic resistor at constant temperature, check whether V/I remains approximately constant.
Electricity Class 10 MCQs with Answers
1. How should an ammeter be connected?
A. In series
B. In parallel across the resistor
C. Across the battery without a load
D. Outside the circuit
Answer: A. In series. It measures the current flowing through that circuit path.
2. What is the equivalent resistance of two 4 Ω resistors in parallel?
A. 8 Ω
B. 4 Ω
C. 2 Ω
D. 16 Ω
Answer: C. 2 Ω. Two equal resistors in parallel have half the resistance of either resistor.
3. Which quantity is measured in kilowatt-hours?
A. Current
B. Resistance
C. Power
D. Energy
Answer: D. Energy. A kilowatt-hour is power multiplied by time.
Assertion–Reason Practice
Assertion: Adding another resistor in parallel reduces the equivalent resistance of a resistor network.
Reason: The additional branch provides another path for current, increasing the network’s conductance.
Answer: Both statements are true, and the reason correctly explains the assertion.
Electricity Class 10 Case-Based Questions
Case Study: Two Resistors Across a Battery
A 6 Ω resistor and a 3 Ω resistor are connected in parallel across an ideal 6 V battery.
Question 1: What voltage acts across each resistor?
6 V.
Question 2: Find the current through the 6 Ω resistor.
I₁ = V/R₁
I₁ = 6/6
I₁ = 1 A
Question 3: Find the current through the 3 Ω resistor.
I₂ = V/R₂
I₂ = 6/3
I₂ = 2 A
Question 4: Find the total current.
I = I₁ + I₂
I = 1 + 2
I = 3 A
Electricity Class 10 Important Questions
- Define electric current, potential difference and resistance.
- State Ohm’s law and describe the experimental setup.
- Explain how resistance depends on length and cross-sectional area.
- Distinguish resistance from resistivity.
- Derive equivalent resistance for series and parallel combinations.
- Explain why appliances are connected in parallel.
- State Joule’s law of heating and describe its applications.
- Calculate current, power and energy using appropriate formulas.
- Convert electrical energy between joules and kilowatt-hours.
How to Use the Worksheet as a Chapter Test
Attempt the Electricity worksheet without checking the answers. Review mistakes under formulas, circuit connections, unit conversions or calculations. Repeat difficult questions after revising the relevant concept.
Use seconds when calculating energy in joules, and hours when multiplying kilowatts to obtain kilowatt-hours. Check whether a question keeps voltage or current constant before comparing power or heat.
Frequently Asked Questions
What is the difference between current and potential difference?
Current is the rate of charge flow. Potential difference is energy transferred per unit charge between two points. Their units are amperes and volts respectively.
Why do electrons move opposite to conventional current?
Conventional current is defined using positive-charge motion. Electrons carry negative charge, so their drift direction in a metallic conductor is opposite.
Does Ohm’s law apply to every electrical component?
No. It describes ohmic behaviour under constant physical conditions. Components such as diodes do not generally show a constant V/I relationship.
Why is a voltmeter connected in parallel?
It measures the potential difference between two points. Connecting it across a component places its terminals at those two points.
What happens to resistance if a wire’s radius doubles?
If length, material and temperature remain unchanged, its cross-sectional area becomes four times larger. Its resistance therefore becomes one-fourth.
Can a wire be stretched without changing its resistance?
Generally not. Stretching increases length and decreases cross-sectional area. If volume and resistivity remain constant, doubling the length makes resistance four times larger.
Is current used up while passing through a resistor?
No. In a steady series circuit, the same current enters and leaves the resistor. Electrical energy is transferred, while charge is conserved.
Does greater resistance always produce more heat?
The answer depends on the condition. At fixed current, power increases with resistance. At fixed voltage, power decreases as resistance increases.
What is the difference between a kilowatt and a kilowatt-hour?
A kilowatt measures power. A kilowatt-hour measures energy: a 1 kW device operating for 1 hour uses 1 kWh.
How can I improve Electricity Class 10 numericals?
Write the given values, convert units, select the formula, substitute carefully and include the final unit. Check whether the answer makes sense for the circuit arrangement.
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