Question 13 Marks
Draw a diagram of an electric bell. On what principle, does an electric bell work?
Answer
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3 Marks Question
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Question 23 Marks
Explain why, when the current is switched ON through a wire, the needle of a compass kept nearby gets deflected from its North-South position?
Answer
View full question & answer→When an electric current flows through a wire, it produces a magnetic field around the wire.A compass needle aligns itself along the direction of the magnetic field it experiences.Normally, the needle points North-South due to Earth’s magnetic field.When the current is switched ON, the magnetic field of the wire interacts with Earth’s field, causing the needle to deflect from its North-South position.This experiment shows that electric current produces a magnetic effect.
Question 33 Marks
Draw a labelled diagram to show (a) open circuit (b) closed circuit and explain.
Answer
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Question 43 Marks
Explain the following.
(i) Copper and aluminium wires are usually employed for electricity transmission. Explain the reason.
(ii) Explain how does the resistance of a wire vary with its length?
(iii) The tungsten is used almost exclusively for filament of electric lamp. Comment.
(i) Copper and aluminium wires are usually employed for electricity transmission. Explain the reason.
(ii) Explain how does the resistance of a wire vary with its length?
(iii) The tungsten is used almost exclusively for filament of electric lamp. Comment.
Answer
View full question & answer→(i) Due to the low resistance of aluminium and copper both these metals are usually employed for the transmission of electricity.
(ii) The resistance of wire always increases with the increase in its length.
(iii) Since, tungsten has high melting point and high resistance. So, that's why, the tungsten is used exclusively for filament of electric lamp.
(ii) The resistance of wire always increases with the increase in its length.
(iii) Since, tungsten has high melting point and high resistance. So, that's why, the tungsten is used exclusively for filament of electric lamp.
Question 53 Marks
Zubeda made an electric circuit using a cell holder shown in figure, a switch and a bulb. When she put the switch in the ON position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.
Answer
View full question & answer→These may be the reasons by which bulb will not glow
(i) Zubeda may not have arranged the cells in a particular manner, i.e. terminals of cell may not be in alternate form.
(ii) The bulb used by Zubeda may be a fused one.
(iii) The connecting wire in cell holder may not be attached properly.
(i) Zubeda may not have arranged the cells in a particular manner, i.e. terminals of cell may not be in alternate form.
(ii) The bulb used by Zubeda may be a fused one.
(iii) The connecting wire in cell holder may not be attached properly.