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General Science›Ch 1: Physics›Electricity Fundamentals

1.11

Electricity Fundamentals

5 min

Mastering Ohm's Law, Circuits, and Power for Exams

1

The Golden Rule of Electricity

Ohm's law states that Voltage is proportional to Current. Resistance limits the flow, while Electric Power measures energy consumption rate.

2

Why Study This?

  • SSC and Railways ask 2-3 direct questions on SI units and formulas.
  • Practical questions on domestic wiring and fuses are common in State exams.
  • Calculating electricity bills (kWh) is a favorite numerical topic.

Memory Hooks

  • V = I x R (Think: VIP Room).
  • Series = Same Current; Parallel = Same Voltage.
  • 1 Unit = 1 kWh (Electricity board measurement).
3

Quantities and Units

QuantitySI UnitFormula
CurrentAmpere (A)I = V/R
ResistanceOhm (Ω)R = V/I
PowerWatt (W)P = V x I
EnergyJoule / kWhE = P x t
4

Component Functions

Resistor

(Limits flow)

Resistor: Limits flowA

Limits flow

Used to control brightness.

Ammeter

(Measures current)

Ammeter: Measures currentA

Measures current

Always connected in series.

Fuse Wire

(Safety device)

Fuse Wire: Safety deviceA

Safety device

Melts during high current.

Voltmeter

(Measures potential)

Voltmeter: Measures potentialA

Measures potential

Connected in parallel.

5

Exam Traps

Fuse wire has high melting point.Fuse wire has low melting point.

It must melt quickly to break the circuit and prevent fire.

kWh is the unit of Power.kWh is the unit of Energy.

Watt is power; Watt multiplied by time is Energy.

Resistance decreases with length.Resistance increases with length.

Resistance is directly proportional to the length of the wire.

6

Quick Check

Q1.If Voltage is doubled and Resistance is halved, what happens to Current?

Q2.Which device is used to change the resistance in a circuit?

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