question_answer1) (i) The potential difference between two points in an electric circuit is 1 volt. What does it mean? Name a device that helps to measure the potential difference across a conductor. (ii) Why does the connecting cord of an electric heater not glow while the heating element does? (iii) Electrical resistivity's of some substances at 20?C are given below: Answer the following questions using above data: (a) Among silver and copper, which one is a better conductor? Why? (b) Which material would you advise to be used in electrical heating devices and why?View Answer play_arrow
question_answer2) [CBSE Delhi 2008] (a) Name an instrument that measures electric current in a circuit. Define the unit of electric current. (b) What do the following symbols represent in a circuit diagram? (i) (ii) (c) An electric circuit consisting of a 0.5 m long nichrome wire XY, an ammeter, a voltmeter, four cells of 1.5 V each and a plug key was set up. (i) Draw the electric circuit diagram to study the relation between the potential difference maintained between the points 'X' and 'Y' and the electric current flowing through XY. (ii) Following graph was plotted between V and I values using above circuit: What would be the values of? ratios when the potential difference is 0.8 V, 1.2 V and 1.6 V, respectively? What conclusion do you draw from these values? [CBSE Delhi 2008]View Answer play_arrow
question_answer3) Explain the following: (i) Why is the tungsten used almost exclusively for filament of an electric lamp? (ii) Why are the elements of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal? (iii) Why is the series arrangement of appliances not used for domestic circuits? [NCERT, CBSE (AI) 2008] (iv) How does the resistance of a wire vary with its area of cross-section? (v) Why are copper and aluminium wires usually employed for electric energy transmission? [NCERT]View Answer play_arrow
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