Class 10 Science Chapter 12 Electricity
Are you looking for Class 10 Science Chapter 12 Electricity (English Medium) notes and question answers? If yes, you are in the right place. This chapter is one of the most important topics in Class 10 Science and is very useful for school exams, HSLC board exams, and competitive examinations.
In this chapter, you will learn about electric current, electric potential, potential difference, Ohm’s Law, resistance, resistivity, series and parallel combinations of resistors, heating effect of electric current, and electric power. These concepts help students understand how electricity works in our daily life and are important for solving both numerical and theory questions.
The notes and question answers are written in easy and simple English, so every student can understand the chapter without any difficulty. Each topic is explained in a clear and step-by-step manner, making learning easier and revision faster before examinations.
Whether you are preparing for class tests, annual examinations, or the HSLC Board Examination, these notes and solutions will help you strengthen your concepts, improve your problem-solving skills, and score higher marks in Science.
✨ In This Chapter, You Will Get:
- 📖 Easy Chapter Notes
- ❓ Complete Textbook Question Answers
- ⭐ Important Exam Questions
- 📝 Simple Explanations
- 📚 Quick Revision Notes
- 🎯 HSLC Board Exam Preparation
Study Class 10 Science Chapter 12 Electricity (English Medium) regularly to build a strong understanding of electrical concepts and perform confidently in your examinations.
Class 10 Science Chapter 12 Electricity
Selected Questions &Answers
Q. What happens to the ammeter reading if the length of a wire is doubled?
Ans: The ammeter reading becomes half of the previous value.
Q. On which factors does the resistance of a conductor depend?
Ans: It depends on the nature of the material, temperature, and length of the conductor.
Q. Define 1 ampere.
Ans: If one coulomb of charge flows through a conductor in one second, the current is said to be 1 ampere.
Q. Why are the coils of electric toasters and electric irons made of alloys instead of pure metals?
Ans: Alloys have higher resistance than pure metals. Therefore, even a small current produces heat, so they are used.
Q. Between a thick wire and a thin wire of the same material connected to the same source, which allows more current, and why?
Ans: More current flows through the thin wire because it has less resistance than the thick wire.
Q. What determines the rate at which electrical energy is supplied by a current?
Ans: Electrical power.
Q. Write Ohm’s law.
Ans: At constant temperature, the potential difference across the ends of a conductor is directly proportional to the current flowing through it.
Q. How is the life of an electric bulb filament increased?
Ans: By filling the bulb with chemically inert gases like argon and nitrogen.
Q. Name a device that maintains a potential difference in a circuit.
Ans: Battery or electric cell.
Q. If the potential difference across a conductor is reduced to half while resistance remains constant, what happens to the current?
Ans: The current also becomes half.
Q. Define the unit of current.
Ans: The unit of current is the ampere. One ampere is defined as the flow of one coulomb of charge per second.
Q. On which factors does the resistance of a conductor depend?
Ans:
(a) Length of the conductor
(b) Cross-sectional area
Q. Calculate the number of electrons required to make one coulomb of charge.
Ans: Charge of one electron, e = 1.6 × 10-19 C
Number of electrons = 1 / (1.6 × 10-19) = 6.25 × 1018 electrons
Q. How much energy is given to each coulomb of charge passing through a 6 V battery?
Ans: Energy = 6 joules
Q. Why are toaster and iron coils made of alloys instead of pure metals?
Ans: Alloys have higher resistance, so they produce more heat when current flows.
Q. Between a thick and a thin wire of the same material connected to the same source, which carries more current and why?
Ans: The thick wire carries more current because it has lower resistance.
Q. Using table data:
(a) Which is a better conductor, iron or mercury?
(b) Which is the best conductor?
Ans:
(a) Iron has lower resistance than mercury, so it is a better conductor.
(b) Silver has the least resistance, so it is the best conductor.
Q. Why does the heating element of an electric heater glow but the connecting wires do not?
Ans: The heating element has high resistance, so it converts more electrical energy into heat and glows. Connecting wires have low resistance, so they do not glow.
Q. 9600 coulomb of charge flows in 1 hour through a potential difference of 50V. Find the heat produced.
Ans: Heat = V × Q = 50 × 9600 = 480000 J
Q. An electric iron of resistance 20O draws 5A current. Calculate the heat produced in 30 seconds.
Ans: Heat = I²Rt = (5)² × 20 × 30 = 15000 J
Q. What determines the rate of electrical energy consumption?
Ans: Electrical power.
Q. A motor takes 5A current from a 220V line. Find its power and energy consumed in 2 hours. HSLC ’20
Ans: Power = VI = 220 × 5 = 1100 WEnergy = 1100 × 2 hours = 2200 Wh = 2.2 kWh
Q. A wire of resistance R is cut into five equal parts and connected in parallel. What is the ratio R/R’?
(a) 1/25
(b) 1/5
(c) 5
(d) 25
Ans: (d) 25
Q. Which of the following does not represent electric power?
(a) I²R
(b) IR²
(c) VI
(d) V²/R
Ans: (b) IR²
Q. A bulb is rated 220V, 100W. If used at 110V, its power will be:
(a) 100W
(b) 75W
(c) 50W
(d) 25W
Ans: (d) 25W
Q. Two identical wires are connected first in series and then in parallel. What is the ratio of heat produced?
(a) 1:2
(b) 2:1
(c) 1:4
(d) 4:1
Ans: (c) 1:4
Q. How is a voltmeter connected in a circuit to measure potential difference?
Ans: It is always connected in parallel.
Q. A copper wire has a diameter 0.5 mm and a resistivity 1.6 × 10⁻⁸ Om. Find its length for resistance 10O. What happens if the diameter is doubled?
Ans: Using R = pL/A
L = (R × A) / p
A = p(d/2)² = p(0.00025)²
L ˜ 122.7 m
If the diameter is doubled, area becomes four times, so the resistance becomesone-fourth.
Q. Given values of V and I, plot a graph and find the resistance:
I (A): 0.5, 1.0, 2.0, 3.0, 4.0
V (V): 1.6, 3.4, 6.7, 10.2, 13.2
Ans: Resistance ˜ V/I ˜ 3.3 O (average slope)
Q. Five resistors of 0.2O, 0.3O, 0.4O, 0.5O and 12O are connected in series with a 9V battery. How much current flows through the 12O resistor?
Ans: Total resistance, R = 0.2 + 0.3 + 0.4 + 0.5 + 12 = 13.4OCurrent, I = V/R = 9 / 13.4 ˜ 0.67 A
Since in series the same current flows through all resistors, the current through the 12O resistor = 0.67 A
Q. How many 176O resistors are required to get 5A current from a220V line?
Ans: Required total resistance, R = V/I = 220/5 = 44O
Let number of resistors = n
Equivalent resistance = 176/n = 44
So, n = 176/44 = 4
Therefore, 4 resistors are required (connected in parallel)
Q. Find the power used in each case:
(i) Two resistors 1O and 2O connected in series with 6V battery
(ii) Two resistors 12O and 2O connected in parallel with 4V battery
Ans:
(i) Series: R = 1 + 2 = 3O
Power, P = V²/R = 36/3 = 12 W
(ii) Parallel: R = (12×2)/(12+2) = 24/14 = 12/7O
P = V²/R = 16 ÷ (12/7) = 16 × 7/12 ˜ 9.33 W
Q. Two bulbs rated 220V–100W and 220V–60W are connected in parallel. Find the total current drawn.
Ans:
Current = P/V
I1 = 100/220 ˜ 0.45 A
I2 = 60/220 ˜ 0.27 A
Total current = 0.45 + 0.27 = 0.72 A
Q. Which uses more energy: a 250W TV for 1 hour or a 1200W heater for 10 minutes?
Ans:
TV energy = 250 × 1 = 250 Wh
Heater energy = 1200 × (10/60) = 200 Wh
Therefore, TV uses more energy.
Q. A 4O electric heater draws 15A current for 2 hours. Find the rate of heat production. HSLC ’20
Ans:
Power = I²R = (15)² × 4 = 900 W
Q. Explain:
(a) Why tungsten is used as filament in bulbs?
Ans: Tungsten has high resistance and very high melting point.
(b) Why alloys are used in heating devices?
Ans: Alloys have higher resistance and produce more heat.
(c) Why series arrangement is not used in household circuits?Ans:
(i) Same current flows through all devices
(ii) Total resistance is high
(iii) Cannot operate devices independently
(iv) Wastage of electricity
(d) How does resistance vary with cross-sectional area?
Ans: Resistance is inversely proportional to cross-sectional area.
(e) Why copper and aluminium are used for wiring?
Ans: They have very low resistance and conduct electricity easily.
Q. The SI unit of potential difference is:
(a) Volt
(b) Ampere
(c) Joule
(d) None
Ans: (a) Volt
Q. State Ohm’s law.
Ans: At constant temperature, the potential difference is directly proportional to the current.
Q. Define potential difference and give the formula.
Ans: Work done to move a unit charge between two points.
Formula: V = W/Q
Q. Define electric current and its SI unit.
Ans: Flow of charge per second. SI unit: Ampere
Q. On what factors does resistance depend?
Ans: Nature of material and temperature.
Q. How much energy is given per coulomb in a 6V battery? HSLC ’19
Ans: 6 J
Q. A bulb carries 0.5A current for 10 minutes. Find charge. HSLC ’19
Ans:
Q = I × t = 0.5 × (10×60) = 300 C
Q. Practical unit of electrical energy? HSLC ’18
Ans: Kilowatt-hour (kWh)
Q. SI unit of resistivity: HSLC ’15
(a) O
(b) O m
(c) O m?¹
(d) O m²
Ans: (b) O m
Q. 1 kWh means: HSLC ’19
Ans: Energy consumed by 1 kW power in 1 hour = 3.6 × 106 J
Q. A 220V, 100W bulb used at 110V will have power: HSLC ’18
Ans: 25W
Q. A wire is cut into 4 equal parts and connected in parallel. Find the ratio of original to equivalent resistance. HSLC ’15
Ans: Each part = R/4
Parallel equivalent = R/16
Ratio = R : (R/16) = 16:1
Q. How is the life of a bulb filament increased? HSLC ’17
Ans: By filling inert gases like argon and nitrogen inside the bulb.
Multiple Choice Questions (MCQ)
Q. How should a voltmeter be connected in a circuit?
(a) In series with resistance
(b) In parallel with resistance
(c) Can be connected in any way
(d) None of the above
Ans: (b) In parallel with resistance
Q. The instrument used to measure current is:
(a) Voltmeter
(b) Ammeter
(c) Galvanometer
(d) Barometer
Ans: (b) Ammeter
Q. Two identical wires are connected first in series and then in parallel across the same potential difference. The ratio of heat produced is:
(a) 1:2
(b) 2:1
(c) 1:4
(d) 4:1
Ans: (c) 1:4
Q. The SI unit of electric current is:
(a) Ohm
(b) Volt
(c) Watt
(d) Ampere
Ans: (d) Ampere
Q. The SI unit of resistivity is:
Ans: Ohm metre (Om)
Q. If the length of the connecting wire in a circuit is reduced to half, what happens to the ammeter reading?
Ans: Resistance becomes half, so current doubles.
Therefore, the ammeter reading increases (becomes double).
Q. A bulb rated 220V, 100W is used at 110V. Its power will be:
(a) 100W
(b) 75W
(c) 50W
(d) 25W
Ans: (d) 25W
