Resistance MCQs Quiz | Class 10
This quiz on Resistance for Class X Science (Code 086), Unit IV: Effects of Current, covers the definition, unit, and meaning of resistance. Test your knowledge with these multiple-choice questions. Once you complete the quiz, remember to submit your answers and download a detailed answer PDF for future revision.
Understanding Electrical Resistance
Electrical resistance is a fundamental property of materials that opposes the flow of electric current. Imagine water flowing through a pipe; resistance is like the friction that slows the water down. In electrical circuits, this “friction” converts some of the electrical energy into heat.
Definition and Meaning
Definition: Electrical resistance (R) is the opposition offered by a conductor to the flow of electric current (I) through it. It quantifies how strongly a material resists the movement of charge carriers (electrons).
Meaning:
- A material with high resistance means that a large voltage is required to push a small current through it, or for a given voltage, only a small current will flow. Insulators like rubber and plastic have very high resistance.
- A material with low resistance means that a small voltage can push a large current through it. Conductors like copper and silver have very low resistance.
Unit of Resistance
The SI unit of electrical resistance is the Ohm, symbolised by the Greek letter Omega (Ω). One Ohm is defined as the resistance between two points of a conductor when a constant potential difference of 1 volt applied to these points produces a current of 1 ampere.
According to Ohm’s Law, which states that V = I x R (Voltage = Current x Resistance), the unit Ohm can be expressed as Volts per Ampere (V/A).
Factors Affecting Resistance
The resistance of a conductor depends on several factors:
| Factor | Relationship with Resistance | Explanation |
|---|---|---|
| Length (L) | R ∝ L (Directly proportional) | A longer wire offers more resistance because electrons have to travel a greater distance, encountering more obstacles. |
| Area of Cross-section (A) | R ∝ 1/A (Inversely proportional) | A thicker wire (larger area) offers less resistance because there is more space for electrons to flow, reducing collisions. |
| Nature of Material | Depends on resistivity (ρ) | Different materials have different atomic structures and free electron densities, leading to varying abilities to conduct current. For example, copper has low resistivity, while nichrome has high resistivity. |
| Temperature | Increases for metals, decreases for semiconductors | For most metallic conductors, resistance increases with temperature as atoms vibrate more, hindering electron flow. |
This relationship is summarized by the formula: R = ρL/A, where ρ (rho) is the resistivity of the material.
Quick Revision Checklist
- Resistance: Opposition to current flow.
- Unit: Ohm (Ω).
- Ohm’s Law: V = IR.
- Factors: Length (directly proportional), Area of cross-section (inversely proportional), Nature of material (resistivity), Temperature.
Practice Questions (For Self-Study)
Test your understanding further with these questions (answers not provided):
- Why do good conductors have low electrical resistance?
- Explain how the length of a wire influences its resistance.
- If you double the diameter of a wire, what happens to its resistance?
- What is the difference between resistance and resistivity?
- Give two examples of materials with high resistance and two with low resistance, explaining their typical uses.
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