Q1 Define the term current and state its S.I. unit.

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Q2 Define the term electric potential. State it’s S.I. unit.

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Q3 How is the electric potential difference between the two points defined? State its S.I. unit.

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Q4 Explain the statement ‘the potential difference between two points is 1 volt’.

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Q5 (a) State whether the current is a scalar or vector? What does the direction of current convey?

(b) State whether the potential is a scalar or vector? What does the positive and negative sign of potential convey?

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Q6 Define the term resistance. State its S.I. unit.

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Q7 (a) Name the particles which are responsible for the flow of current in a metallic wire.

(b) Explain the flow of current in a metallic wire on the basis of movement of the particles named by you above in part (a).

(c) What is the cause of resistance offered by the metallic wire in the flow of current through it?

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Q8 State Ohm’s law and draw a neat labelled circuit diagram containing a battery, a key, a voltmeter, an ammeter, a rheostat and an unknown resistance to verify it.

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Q9 (a) Name and state the law which relates the potential difference and current in a conductor.

(b) What is the necessary condition for a conductor to obey the law named above in part (a)?

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Q10 (a) Draw a V-I graph for a conductor obeying Ohm’s law.

(b) What does the slope of V-I graph for a conductor represent?

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Q11 Draw a I-V graph for a linear resistor. What does its slope represent?

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Q12 What is an ohmic resistor? Give one example of an ohmic resistor. Draw a graph to show its current – voltage relationship. How is the resistance of the resistor determined from this graph?

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Q13 What are non-ohmic resistors? Give one example and draw a graph to show its current-voltage relationship.

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Q14 Give two differences between an ohmic and non-ohmic resistor

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Q15 Fig. below shows the I-V characteristic curves for two resistors. Identify the ohmic and non-ohmic resistors. Give a reason for your answer.

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Q16 Draw a V – I graph for a conductor at two different temperatures. What conclusion do you draw from your graph for the variation of resistance of conductor with temperature?

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Q17 (a) How does the resistance of a wire depend on its radius? Explain your answer.

(b) Two copper wires are of same length, but one is thicker than the other. Which will have more resistance?

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Q18 How does the resistance of a wire depend on its length? Give a reason of your answer.

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Q19 How does the resistance of a metallic wire depend on its temperature? Explain with reason.

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Q20 Two wires, one of copper and other of iron, are of the same length and same radius. Which will have more resistance? Give reason.

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Q21 Name three factors on which the resistance of a wire depends and state how it is affected by the factors stated by you?

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Q22 Define the term specific resistance and state its S.I. unit.

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Q23 Write an expression connecting the resistance of a wire and specific resistance of its material. State the meaning of symbols used.

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Q24 State the order of specific resistance of (i) a metal, (ii) a semiconductor and (iii) an insulator.

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Q25 (a) Name two factors on which the specific resistance of a wire depends?

(b) Two wires A and B are made of copper. The wire A is long and thin while the wire B is Short and thick. Which will have more specific resistance?

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Q26 Name a substance of which the specific resistance remains almost unchanged by the increase in temperature

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Q27 How does specific resistance of a semi-conductor change with the increase in temperature?

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Q28 How does (a) resistance, and (b) specific resistance of a wire depend on its (i) length, and (ii) radius?

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Q29 (a) Name the material used for making the connection wires. Give reason for your answer.

(b) Why should a connection wire be thick?

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Q30 Name the material used for making a fuse wire. Give a reason.

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MULTIPLE CHOICE TYPE (Exercise 8a)

Q1 Which of the following is an ohmic resistance?

(a) LED
(b) Junction diode
(c) Filament of a bulb
(d) Nichrome wire

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Q2 For which of the following substances, resistance decreases with increase in temperature?

(a) Copper
(b) Mercury
(c) Carbon
(d) Platinum

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NUMERICAL (8a)

Q1 Define the term current and state its S.I. unit.

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Q1 In a conductor, 6.25 × 10¹⁶ electrons flow from its end A to B in 2 s. Find the current flowing through the conductor. (e = 1.6 × 10^-19 C)

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Q2 A current of 1.6 mA flows through a conductor. If charge of an electron is -1.6 x 10-19 coulomb, find the number of electrons that will pass each second through the cross section of that conductor.

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Q3 Find the potential difference required to flow a current of 200 mA in a wire of resistance 20 ohm.

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Q4 An electric bulb draws 1.2 A current at 6.0 V. Find the resistance of filament of bulb while glowing.

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Q5 A car bulb connected to a 12 volt battery draws 2 A current when glowing. What is the resistance of the filament of the bulb? Will the resistance be more, same or less when the bulb is not glowing.

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Q6 Calculate the current flowing through a wire of resistance 5 Ω connected to a battery of potential difference 3V.

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Q7 In an experiment of verification of Ohm’s law, following observations are obtained.

Draw a characteristic V-I graph and use this graph to find:

(a) potential difference V when the current I is 0.5 A.
(b) current I when the potential difference V is 0.75 V.
(c) resistance in circuit

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Q8 Two wires of the same material and same length have radii 1 mm and 2 mm respectively. Compare (i) their resistances (ii) their specific resistance.

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Q9 A given wire of resistance 1 Ohm is stretched to double its length. What will be its new resistance?

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Q10 A wire of resistance 3 Ohm and length 10 cm is stretched to length 30 cm. Assuming that it has a uniform cross-section, what will be its new resistance?

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Q11 A wire of resistance 9 Ohm having length 30 cm is tripled on itself. What is its new resistance?

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Q12 What length of copper wire of specific resistance 1.7 x 10^-8 ohm m and radius 1 mm is required so that its resistance is 1 ohm.

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Q13 The filament of a bulb takes a current 100 mA when potential difference across it is 0.2 V. When the potential difference across it becomes 1.0 V, the current becomes 400 mA. Calculate the resistance of filament in each case and account for the difference.

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