The chapter on "Electricity" is assigned a weightage of \(7\) marks, highlighting its significance in the overall curriculum. Understanding this chapter will enhance to know how basic electrical components connect and their function.
Also to prepare effectively for related exam questions. It is essential to grasp the various types of electrical circuits, components effects, and their applications. Focusing on these concepts will greatly benefit both academic performance and practical application in physics.
- \(1\) mark - Two questions
- \(5\ \)mark - One question
Learning outcomes:
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Understanding key concepts: Grasp the basic principles of electric current, voltage, and resistance.
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Applying Ohm’s Law: Use the relationship between voltage, current, and resistance to solve problems.
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Analyzing circuits: Distinguish between series and parallel circuits and analyze their behaviour.
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Calculating power and energy: Compute electrical power and energy consumption in various circuits.
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Heating effect of electric current: Understand the heating effect of electric current and its applications (e.g., electric heaters, fuse).
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Mathematical applications: Solve problems related to Ohm’s Law and circuit analysis.
Electricity formulae - At a glance:
| Physical quantity | Symbol | Definition | Formula | SI Unit | Unit Symbol |
| Electric charge | \(Q\) or \(q\) | Basic fundamental properties of all matter | \(Q\ =\ ne\) | \(coulomb\) |
\(C\)
|
| Electric current | \(I\) | Rate of flow of electric charge through a conductor | \(I\ =\ \frac{Q}{t}\) | \(ampere\) | \(A\) |
| Potential difference | \(V\) | Work done to move unit charge between two points | \(V\ =\ \frac{W}{Q}\) | \(volt\) | \(V\) |
| Ohm's law | - | States that current is directly proportional to voltage at constant temperature | \(V\ =\ IR\) | \(volt\) | \(V\) |
| Resistance | \(R\) | Opposition offered by a conductor to the flow of current | \(R\ =\ \frac{V}{I}\) | \(ohm\) | \(\Omega\) |
| Resistivity | \(\rho\) | Intrinsic property of a material that opposes current flow | \(\rho\ =\ \frac{RA}{L}\) | \(ohm-metre\) | \(\Omega\ m\) |
| Resistance of a conductor | \(R\) | Resistance depends on material, length, and area of the conductor | \(R\ =\ \frac{\rho\ L}{A}\) | \(ohm\) | \(\Omega\) |
| Equivalent resistance in series | \(R_s\) | Total resistance when resistors are connected end-to-end | \(R_s\ =\ R_1\ +\ R_2\ +\ R_3\ +\ . . .\) | \(ohm\) | \(\Omega\) |
| Equivalent resistance in parallel | \(R_p\) | Combined resistance when resistors are connected across the same voltage | \(\frac{1}{R_p}\ =\ \frac{1}{R_1}\ +\ \frac{1}{R_2}\ +\ \frac{1}{R_3}\ +\ . . .\) | \(ohm\) | \(\Omega\) |
| Joule's law of heating | \(H\) | Heat generated when current flows through a resistor |
\(H\ =\ I^2Rt\)
\(H\ =\ VIt\)
\(H\ =\ \frac{V^2t}{R}\)
|
\(joule\) | \(J\) |
| Electric Power | \(P\) | Rate at which electrical energy is consumed or converted |
\(P\ =\ VI\)
\(P\ =\ I^2R\)
\(P\ =\ \frac{V^2}{R}\)
|
\(watt\) | \(W\) |
| Electrical energy | \(E\) | Energy consumed by an electrical appliance when it operates | \(E\ =\ P\ \times\ t\) | \(watt-second\) | \(Ws\) |
Important constants and conversions:
| Quantity | Definition | Relation |
| Electronic charge | Charge carried by a single electron | \(e\ =\ -\ 1.6\ \times\ 10^{-16}\ C\) |
| \(1\ coulomb\) | The quantity of charge transferred in one second by a current of one ampere | \(1\ C\ =\ 6.25\ \times\ 10^{18}\ electrons\) |
| \(1\ ampere\) | Current due to flow of one coulomb charge per second | \(1\ A\ =\ 1\ C/s\) |
| \(1\ volt\) | Potential difference when one joule of work is done per coulomb | \(1\ V\ =\ 1\ J/C\) |
| \(1\ ohm\) | Resistance allowing one ampere current at one volt | \(1\ \Omega\ =\ 1\ V/A\) |
| \(1\ watt\) | Power when one joule of energy is used per second | \(1\ W\ =\ 1\ J/s\) |
| \(1\ kilowatt\) | Commercial unit of power | \(1\ kW\ =\ 1000\ W\) |
| \(1\ kilowatt-hour\) | Commercial unit of electrical energy | \(1\ kWh\ =\ 3.6\ \times\ 10^6\ J\) |