1. What is the unit of resistance ?
Memory: Ohm is the practical and SI unit of resistance.
2. The electrical resistance of insulators is ?
- Very high
- Very low
Memory: Resistance of insulators is very high due to the fact that, it has very few free electrons and strongly opposes the follow of electron.
3. What is the cause of resistance ?
- Movement of free electrons
- Movement of ions
- collision of ions and free electrons
Memory: When free electrons moving through a conductor, collision occur between free electrons and ions of the metal (of which it is made of). Results in, a hindrance or resistance creates in the path of flow of electrons.
4. SI unit of resistance is ?
Memory: SI unit of resistance is “Ohm”.
5. On what factors does the resistance of a conductor depend on ?
- Length of the conductor
- Cross-sectional area of the conductor
- Material of the conductor
- All of the above
Memory: Resistance of a conductor is defined mathematically as, R=ρ*L/A. Where,
- R = Resistance
- ρ = The nature of the material.
- L = Length of the conductor.
- A =Area of the conductor.
6. Electrical resistivity of a given metallic wire depends upon ?
- Nature of the material
- Length of the material
- Width of the material
- None of the above
Memory: Resistivity is also known as specific resistance of the material having unit length and unit cross-sectional area.
The resistance between opposite faces of a unit cube of that material.
7. Three resistances each of R ohm connected in such a way to form a triangle. The resistance between any two points of the triangle will be ?
- R Ω
- 3/2 Ω
- 3 Ω
- 2/3 Ω
Memory: It’s answers can be found using series-parallel combination of resistances.
8. Find the equivalent resistance between points a and b of the above circuit ?
- 5 Ω
- 10 Ω
- 3.33 Ω
- 2 Ω
Memory: The answer can be found by using “series-parallel combination” of resistances.
9. An electric bulb is rated 220V and 100W . What is the resistance of the filament ?
- 200 Ω
- 484 Ω
- 584.5 Ω
- 220 Ω
Memory: The answer can be found by using the following formula – (R = V^2/W).
10. Reciprocal of specific resistance is ?
- Specific reluctance
- Specific capacitance
- Specific conductance
- Specific inductance
Memory: Specific resistance is also known as
Resistivity and it’s the reciprocal of conductivity.
It is measured in ohm-m.
11. The temperature co-efficient of resistance of conductors is ?
- Varied with change in temperature
Memory: Positive temperature means, it’s value does not change with the change in temperature.