Problem Sheet – I

Current Electricity and Heating Effects

1. In the Ohm’s law verification circuit shown below, find out the value of resistance R if you are given that the voltage drop across R is 5V and the current through the circuit is 10A.

2. State Ohm’s law and also express it mathematically.
3. What do you mean by resistance? What are the factors on which it depends?
4. Define resistivity.
5. Derive the laws of series and parallel connection of resistances.
6. Find out the equivalent resistance in each case:-

                        a)

    where R₁  = 2 ohm

    R2 = R3 = R4 = 1ohm

b)  

            where R1= R4 = R5 = 2 ohm

            R2 = R3= 1 ohm

7. What do you mean by potential and potential difference?
8. What is electric power? What is its S.I. unit?
9. Explain heating effect of electric current and formulate mathematically.
10. Give some practical examples of heating effect of current.
11.  A potential difference of 250 volts is applied across a resistance of 500 ohms in an electric iron. Calculate the current, the heat energy produced in Joules in 10 seconds.
12. A resistance of 40 ohms and one of 60 ohms are connected in series across a 200V battery. Find the heat in calories produced by this combination in 0.5 minutes.
13. Explain the action of the following in domestic wiring a) electric fuse, b) earthing.
14. What is the commercial unit of electrical energy? Derive its relation with the S.I. unit.
15. A current of 4 amperes flows through a 12V battery for 10 minutes. How much energy is consumed during this time? 

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