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Name the material which is used for making the filaments of an electric bulb.
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The heat produced by passing an electric current through a fixed resistor is proportional to the square of:
(a) magnitude of resistance of the resistor
(b) temperature of the resistor
(c) magnitude of current
(d) time for which current is passed
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The current passing through an electric kettle has been doubled. The heat produced will become:
(a) half
(b) double
(c) four time
(d) one-fourth
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An electric fuse works on the:
(a) chemical effect of current
(b) magnetic effect of current
(c) lighting effect of current
(d) heating effect of current
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The elements of electrical heating devices are usually made of:
(a) tungsten
(b) bronze
(c) nichrome
(d) argon
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The heat produced in a wire of resistance 'x' when a current 'y' flows through it in time 'z' is given by:
(a) x2 × y × z
(b) x × z × y2
(c) y × z2 × x
(d) y × z × x
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Which of the following characteristic is not suitable for a fuse wire?
(a) thin and short
(b) thick and short
(c) low melting point
(d) higher resistance than rest of wiring
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If the current flowing through a fixed resistor is halved, the heat produced in it will become:
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The electrical resistivities of four materials P, Q, R and S are given below:
| P | `6.84xx10^8`Ωm |
| Q | `1.70xx10^8`Ωm |
| R | ` 1.0xx10^15`Ωm |
| s | `11.0xx10^-7`Ωm |
Which material will you use for making: (a) heating element of electric iron (b) connecting wires of electric iron (c) covering of connecting wires? Give reason for your choice in each case.
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How does the wire in the filament of a light bulb behave differently to the other wires in the circuit when the current flows?
What property of the filament wire accounts for this difference?
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Two exactly similar heating resistances are connected (i) in series, and (ii) in parallel, in two different circuits, one by one. If the same current is passed through both the combinations, is more heat obtained per minute when they are connected in series or when they are connected in parallel? Give reason for your answer.
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An electric iron is connected to the mains power supply of 220 V. When the electric iron is adjusted at ‘minimum heating' it consumes a power of 360 W but at 'maximum heating’ it takes a power of 840 W. Calculate the current and resistance in each case.
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Which electric heating device in your home do you think have resistors which control the flow of electricity?
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Write the mathematical expression for Joule’s law of heating.
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Compute the heat generated while transferring 96000 coulombs of charge in two hours through a potential difference of 40 V.
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Write two devices based on the heating effect of electric current.
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An electric iron draws a current of 4 A when connected to 220 V mains. Its resistance must be:
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A fuse wire repeatedly gets burnt when used with a good heater. It is advised to use a fuse wire of:
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A current of 1 A is drawn by a filament of an electric bulb. Number of electrons passing through a cross-section of the filament in 16 seconds would be roughly:
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The heating element of an electric iron is made up of:
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