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Define the unit of electric current.

What is he minimum resistance which can be made using five resistors each of ?

Draw a circuit diagram of a circuit consisting of a cell of 1.5V, 10 Ω resistors and a plug key all connected in series.

Write a mathematical expression for Joule’s law of heating effect of current. Name one device which works on this principle.

Should the resistance of an ammeter be low or high? Give reason.

In an experiment to study the relationship between the potential difference across a resistor and the current through it, a student recorded the following observations:

Find in which one of the above sets of readings the trend is different from others and must be rejected. Calculate the mean value of resistance of the resistor based on the remaining sets of readings.

Two electric bulbs A and B are marked 40 W – 220 V and 60 W – 220 V respectively. Which one of the two has a greater resistance?

a. Table gives the resistivity of three materials in (in Ω m) A, B, C.

Which one of them is the best conductor? And which is an insulator and why?

b. A wire of resistivity P is stretched to twice its length. What will be its new resistivity?

How can three resistance of 2, 3 and 6 ohms be connected so as to give a total resistance of 1 ohm?

The resistance of a metal wire of length 1 m is 25 Ω at 20° C. If the diameter of the wire is 0.3 mm, What must be the resistivity of metal at that temperature?

How is an ammeter and a voltmeter connected in a circuit and why?

Why does the cord of an electric heater not glow while the heating element does?

Study the following circuit and answer the following questions.

i. State the type of combination of the two resistors in the circuit.

ii. How much current is flowing through (a) 10 Ω register?

iii. What is the ammeter reading?

Name two safety measures commonly used in domestic electric circuits and appliances. What precautions should be taken to avoid the overloading of domestic electric circuit?

How does use of a fuse wire protect electrical appliances?

Why is parallel arrangement used in domestic wiring?

State Ohm’s law? How can it be verified experimentally? Does it hold well under all conditions? Comment.

What is electrical resistivity of a material? What is its unit? Describe an experiment to study the factors on which the resistance of conducting wire depends.

How will you conclude that the same potential difference (voltage) exists across three resistors connected in a parallel arrangement to a battery?

Three bulbs each having power P are connected in series in an electric circuit. In another circuit another set of three bulbs of same power are connected in parallel to the same source.

i. Will the bulbs in both the circuits glow with the same brightness? Justify your answer.

ii. Now let one bulb in each circuit get fused. Will the rest of the bulbs continue to glow in each circuit? Give reason.

How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistances in series connected to a battery?

What is Joule’s heating effect? How can it be demonstrated experimentally? List its four applications in daily life.