Current of Electricity Main Note

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Definition

Electric Current is the rate of flow of electric charge (per unit time) #PhysicsDefinitions

Formulae

$I = \frac{Q}{t}$$ where I = current (A) Q = charge (C) t = time taken (s)

Another variation: $I=\frac{P}{V}$ where P is power in watt

SI unit for current = Ampere (A) or Coulomb (C) per second (s)

• 1 ampere → is the electric current produced when 1 coulomb of charge passes a point in 1 second

1 coulomb is not equal to 1 electron

Note

Coulomb → derived unit. Ampere → SI based unit 1 coulomb = amount of charge when 1 ampere of current → flows for 1 second. 1 coulomb → approx. equal to charge of $6.25\times 10^{18}$ protons. charge on each proton → is about $1.60\times 10^{-19}C$

Formulae

Additional formulae: Rate of flow of electrons along wire. $\frac{I}{chargeonelectron}$ flows in opposite direction to the current. conventional current is opposite to electron flow

Formulae

Additional Formulae: Formula for charge $Q=numberofelectronsflowing\times chargeofoneelectron(1.6\times 10^{-19})$ When you add this to the current formula: $I=\frac{numberofelectronsflowing\times chargeofoneelectron}{time}$

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Conventional Current and Electron Flow

Conventional Current and Electron Flow

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Electromotive Force and Potential Difference

Electromotive Force and Potential Difference

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Resistance

Resistance

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Understanding

A dry cell is a single electrochemical cell with a paste electrolyte, typically producing 1.5V (e.g., zinc-carbon, alkaline cells). A battery consists of two or more cells connected in series (to increase voltage) or parallel (to increase capacity). In O-Level Physics, the total EMF in series is the sum of individual EMFs, while in parallel, it remains the same as one cell.

Formulae

Linked formulas: Work Done and Power $P=\frac{W}{t}=\frac{E}{t}$ P = power (W) W = Work done(W) E = energy transferred (j) t = time taken (s)