Learn Class 10 Physics Unit 14 – Current Electricity with easy-to-understand notes. This chapter explains electric current, potential difference, electromotive force (e.m.f.), Ohm’s Law, resistance, conductors and insulators, series and parallel circuits, electric power, Joule’s law, DC & AC, and electrical safety. These notes help students prepare for exams quickly while understanding practical uses of electricity.
Important MCQs – Unit 14 Current Electricity
1. An electric current in conductors is due to the flow of:
(a) positive ions
(b) negative ions
(c) positive charges
(d) free electrons ✅
2. The SI unit of electric current is:
(a) Volt
(b) Ohm
(c) Ampere ✅
(d) Watt
3. According to Ohm’s Law, current is directly proportional to:
(a) Resistance
(b) Power
(c) Potential difference ✅
(d) Energy
4. A potential difference of 1 volt means:
(a) 1 joule per ampere
(b) 1 joule per coulomb ✅
(c) 1 coulomb per joule
(d) 1 ampere per volt
5. What is the function of a source of e.m.f.?
(a) Converts electrical energy into heat
(b) Measures electric current
(c) Converts non-electrical energy into electrical energy ✅
(d) Increases circuit resistance
Short Questions – Unit 14 Current Electricity
1. What is electric current?
Answer:
Electric current is the rate of flow of electric charge through any cross-section of a conductor. It shows how fast charges are moving in a circuit.
2. What is conventional current?
Answer:
Conventional current is the flow of positive charge in a circuit. It is opposite in direction to the actual flow of electrons, which are negative charges.
3. Define e.m.f.
Answer:
Electromotive force (e.m.f.) is the total energy supplied by a battery or source to move one coulomb of charge from the negative terminal to the positive terminal.
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It shows how much energy the source provides to each unit of charge.
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SI unit of e.m.f. is Volt (V).
4. State Ohm’s Law
Answer:
Ohm’s Law states that current (I) through a conductor is directly proportional to the potential difference (V) across it, provided the temperature and physical conditions remain constant.
Formula (copy-paste friendly):
I = V / R
Where:
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I = Current (Ampere)
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V = Potential difference (Volt)
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R = Resistance (Ohm)
This means:
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If voltage increases, current increases (for same resistance).
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If resistance increases, current decreases (for same voltage).
5. What is the difference between conductors and insulators?
Answer:
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Conductors: Materials that allow free movement of electrons, so electricity can pass through them easily. Examples: copper, aluminum, silver.
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Insulators: Materials that do not allow electrons to move freely, so they block the flow of electricity. Examples: rubber, glass, plastic.
Long Questions – Unit 14 Current Electricity
Q2: What is Electromotive Force (e.m.f.)?
Definition:
Electromotive force (e.m.f.) is the total energy supplied by a battery or cell to move one coulomb of positive charge from its negative terminal to its positive terminal inside the battery.
- Note: It is not a force, but a kind of energy per unit charge.
Explanation:
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A battery converts chemical energy into electrical energy.
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Inside the battery, this energy pushes positive charges from the negative terminal to the positive terminal.
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This buildup of energy allows charges to flow in an external circuit when connected.
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The e.m.f. creates the potential difference required for current to flow.
Mathematical Formula:
e.m.f. (E) = W / Q
Where:
-
E = Electromotive force (in volts)
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W = Work done or energy supplied (in joules)
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Q = Charge (in coulombs)
Numerical Example:
If a 2 V battery moves 10 coulombs of charge:
W = E × Q = 2 V × 10 C = 20 joules
This means the battery supplies 20 joules of energy to move 10 coulombs of charge. ✅
Unit of e.m.f.:
-
SI unit of e.m.f. is Volt (V).
-
1 Volt = 1 Joule per Coulomb
Summary:
Electromotive force (e.m.f.) is the energy provided by a cell or battery to move one coulomb of charge through the internal and external circuit.
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Measured in volts
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Calculated using E = W / Q
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Explains how a battery performs work to create current by moving charges from low to high potentia
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