# Class 10 Electricity Previous Years Questions

Previous Years Questions Notes Important Questions**Electricity Previous Years Questions**

- Define 1 kilowatt hour.
**[1 mark] [CBSE 2019]** **[1 mark] [CBSE 2020]**- 10
^{-6}A and 10^{-9}A respectively - 10
^{-3}A and 10^{-6}A respectively - 10
^{-3}A and 10^{-9}A respectively - 10
^{-6}A and 10^{-3}A respectively

- 10
- A cylindrical conductor of length ‘l’ and uniform area of cross-section ‘A’ has resistance ‘R’. Another conductor of length 2.5 l and resistance 0.5 R of the same material has area of cross-section:
**[1 mark] [CBSE 2020]**- 5 A
- 2.5 A
- 0.5 A
- 1/5 A

- Define the term electrical resistivity of a material.
**[1 mark] [CBSE 2019]** - Consider the scale of a voltmeter shown in the diagram and answer the following questions:
- What is the least count of the voltmeter?
- What is the reading shown by the voltmeter?
- If this voltmeter is connected across a resistor of 20 Ω, how much current is flowing through the resistor.
**[2 marks] [CBSE 2019]**

- The values of current (I) flowing through a given resistor (R), for the corresponding values of potential difference (V) across the resistor are as given below :

V(volts) | 0.5 | 1.0 | 1.5 | 2.0 | 2.5 | 3.0 | 4.0 | 5.0 |
---|---|---|---|---|---|---|---|---|

I(Amperes) | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.8 | 1.0 |

Plot a graph between current (I) and potential difference (V) and determine the resistance (R) of the resistor.** [2 marks] [CBSE 2018]**

**7. **Show how would you join three resistors each of resistance 9 Ω so that the equivalent resistance of the combination is (i) 13.5 Ω (ii) 6 Ω?** [3 marks] [CBSE 2018] **

**8. a.** Write Joule’s law of heating.

**b.** Two lamps, one rated 100 W; 220 V, and the other 60 W; 220 V, are connected in parallel to electric mains supply. Find the current drawn by two bulbs from the line, if the supply voltage is 220 V. ** [3 marks] [CBSE 2018]**

** ** **9.** **a.** List the factors on which the resistance of a conductor in the shape of a wire depends.

**b.** Why are metals good conductor of electricity whereas glass is a bad conductor of electricity ?Give reason.

**c.** Why are alloys commonly used in electrical heating devices? Give reason. ** [CBSE 2018] [3 Marks]**

**10. a. **Three resistors of resistances R_{1}, R_{2} & R_{3} are connected **(i)** in series , & **(ii) **in parallel. Write expressions for the equivalent resistance of the combination in each case.

**b.** Two identical resistors of 12 Ω each are connected to a battery of 3 V. Calculate the ratio of the power consumed by the resulting combinations with minimum resistance & maximum resistance. ** [CBSE 2019] [5 Marks]**

**11. a. **Write the relation between resistance & electrical resistivity of the material of a conductor in the shape of a cylinder of length ‘l’ & area of cross section ‘A’ . Hence derive the S.I. unit of electrical resistivity.

**b. **Resistance of a metal wire of length 5 m is 100 Ω. If the area of cross section of the wire is **3 x** **10**^{-7} m^{2}, calculate the resistivity of the metal. ** [CBSE 2019] [5 Marks]**

**12. a. **Two lamps rated 100 W, 220 V& 10 W , 220 V are connected in parallel to 220 V supply , calculate the total current through the circuit.

**b. **Two resistors x & y of resistances 2 Ω & 3 Ω respectively are first joined in parallel & then in series . In each case the voltage supplied is 5 V.

**(i) **Draw circuit diagrams to show the combination of resistors in each case.

**(ii) **Calculate the voltage across the 3 Ω resistor in the series combination of resistors. ** [CBSE 2020] [5 Marks]**

**13. a. **State ohm’s law.

**b. **How is an ammeter connected in an electric circuit?

**c. **The power of a lamp is 100 W. Find the energy consumed by it in 1 minute.

**d. **A wire of resistance 5 Ω is bent in the form of a closed circle. Find the resistance between two points at the ends of any diameter of the circle. ** [5 marks] [CBSE 2020**]

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