Page 65 - CHAPTER-1 (Electricity)

CHAPTER 1

ELECTRICITY

20. A lamp draws a current of 0.5 A when it is connected to a 60 V

source. What is the resistance of the lamp?

21. Why is a series arrangement not used for connecting domestic

electrical appliances in a circuit?

22. A torch bulb is rated at 1.5 V, 500 mA. Find its resistance.

23. How can we define power for an electrical appliance. What are its

SI units?

Long Answer Type (5 Marks)

1. (a)Express Ohm's law by a mathematical formula.

(b) Draw a circuit diagram to verify Ohm's law.

(c) Present the relationship between the voltage applied across a

conductor and the current flowing through it graphically.

2. State Ohm's law. Express it mathematically. Define SI unit of

resistance. Derive an expression for the equivalent resistance of

three resistors R1, R2 and R3 connected in series (or in parallel).

3. (a)Express Ohm's law both by a mathematical formula and by a

graph line.

(b)State SI units of (i) resistance and (ii) resistivity.

(c)What will be the equivalent resistance of two resistors R1 and R2

(i) connected in series and (ii) connected in parallel.

(a)What is meant by saying that the potential difference between

two points is 1 volt? Name a device that helps to measure the

potential difference across a conductor.

(b)Why does the connecting cord of an electric heater not glow hot

while the heating element does ?

(c)Electrical resistivities of some substances at 20°C are given

below:

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