# Class 10 Physics Current Electricity 14.4. By applying a potential difference of 10 \mathrm{~V} across a conductor a current of 1.5 A passes through it. How much energy would be obtained from the current in 2 minutes?Ans. (1800 J)

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##### 14.4. By applying a potential difference of 10 \mathrm{~V} across a conductor a current of 1.5 A passes through it. How much energy would be obtained from the current in 2 minutes?Ans. (1800 J)

Example: 13.6 What would be the resistance of the above bar at 500^{\circ} \mathrm{C} ?

13.7 Describe a circuit which will give a continuously var ying potential.

14.11. A resistor of resistance 5.6 \Omega is connected across a battery of 3.0 \mathrm{~V} by means of a wire of negligible resistance. A current of 0.5 A passes through the resistor.Calculate(a) Power dissipated in the resistor.(b) Total power produced by the battery.(c) Give the reason of difference between these two quantities.Ans. [(a) 1.4W(b) 1.5 \mathrm{~W} (c) some power is lost by the internal resistance of the battery]

13.10 Ten resistances of different value are connected in parallel. If the p.d.across one of them is 5 \mathrm{~V} . what is the p.d. across the remalning nine resistors?

13.6 When a metal object is heated. both its dimensions and fts resistlvity increase. Is the increase in resistivity likely to be a consequence of the increase in length?

Example 14.1: If 0.5 Ccharge passes through a wire in 10 \mathrm{~s} then what will be the value of current flowing through the wire?

13.2 Do bends in a wire affect its electrical resistance? Explain.

14.4. How can we differentiate between e.m.f. and potential difference?

13.19 A water heater that wlll deliver 1 \mathrm{~kg} of water per minute is required. The water is supplied at 20^{\circ} \mathrm{C} and an output temperature of 80^{\circ} \mathrm{C} is desired. What should be the resistance of the heating element in the water if the line voltage is 220 \mathrm{~V} ?

Example: 13.9 A battery of 6 volts is connected to two resistors of 3 \Omega and 2 \Omega joined together In serles. Find the current through the clrcult and the potentlal drop across each resistor.(Ag.13.5.)Fig 13.5

13.2 Acharge of 90 \mathrm{C} passes through a wire in 1 hour and 15 minutes. What is the current in the wire?(Ans: 20 \mathrm{~mA} )

14.6. Two resistances of 6 \mathrm{k} \Omega and 12 \mathrm{k} \Omega are connected in parallel. A 6 \mathrm{~V} battery is connected across its ends find the values of the following quantities:(a) Equivalent resistance of the parallel combination.(b) Current passing through each of the resistances.(c) Potential difference across each of the resistance.Ans. [(a) 4 \mathrm{k} \Omega (b) 1 \mathrm{~mA} 0.5 \mathrm{~mA} (c) 6 \mathrm{~V} ]

14.3. What do we mean by the term e.m.f? Is it really a force? Explain.

14.8. From your experience in watching cars on the roads at night are automobile headlamps connected in series or in parallel.

14.11. Determine the equivalent resistance of series combination of resistors.

14.1. A current of 3 \mathrm{~mA} is flowing through a wire for 1 minute. What is the charge flowing 10^{-3} \mathrm{C} through the wire? AnsAns. (180

13.4 A rectangular bar of iron is 2.0 \mathrm{~cm} by 2.0 \mathrm{~cm} in cross section and 40 \mathrm{~cm} long. Calculate its resistance if the resistivity of iron is 11 \times 10^{-3} \Omega \mathrm{m} .(Ans: 1.1 \times 10^{-4} \Omega )

13.3 A current of 6 \mathrm{~A} is drawn from a 120 \mathrm{~V} line. What power is being developed? How much energy in joule and in Kwt is expended if the current is drawn steadlly for one week

13.4 Why does the resistance of a conductor rises with the rise in temperature?

13.8 Find the current and power dissipated in each resistance of the circuit shown in Fig. P.13.8.Fig.P. 13.8(Ans: 0.8 \mathrm{~A} 1.4 \mathrm{~A} 2.2 \mathrm{~A} 0.64 \mathrm{~W} 1.96 \mathrm{~W} 3.92 \mathrm{~W} \& 9.68 \mathrm{~W} )

14.5. Two resistances of 2 \mathrm{k} \Omega and 8 \mathrm{k} \Omega are joined in series if a 10 \mathrm{~V} battery is connected across the ends of this combination find the following quantities:(a) The equivalent resistance of the series combination.(b) Current passing through each of the resistances.(c) The potential difference across each resistance.Ans. [(a) 10 \mathrm{k} \Omega (b) 1 \mathrm{~mA} (c) 2 \mathrm{~V} 8 \mathrm{~V}]

Example 13.1 A current of 2.4 amp is nowing in a wlre. How many electrons pass a given point in the wire in one second ir the charge on an electron is 1.6 \times 10^{-19} coulomb.

(b) What is the current in 8 \Omega resister if the potentlal diference of 12 \mathrm{~V} is applied to the netivork?

14.6. In order to measure voltage in a circuit voltmeter is always connected in parallel. Discuss.

13.1 A certain battery is rated at 80 ampere hour. How many coulomb of charge can this battery supply

Example: 13.8 A water heater draws 30 A from a 220 volts power source 15 metres away. What is the minimum cross section of the copper wire that can be used if the voltage is not to be lower than 210 volts at the heater?

14.3. Can current flow in a circuit without potential difference?