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प्रश्न
How does the resistance of a wire vary with its area of cross-section?
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उत्तर
Resistance (R) of a wire is inversely proportional to its area of cross-section (A),
`"R" ∝ 1/"A"`
i.e., when the area of cross section increases, resistance decreases, or vice versa.
संबंधित प्रश्न
How does the resistance of a wire vary with its:
diameter?
What is meant by the heating effect of current?
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
The elements of electrical heating devices are usually made of:
(a) tungsten
(b) bronze
(c) nichrome
(d) argon
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.
Heat energy is being produced in a resistance in a circuit at the rate of 100 W. The current of 3 A is flowing in the circuit. What must be the value of the resistance?
Solve the following example.
Two tungsten bulbs of wattage 100 W and 60 W power work on 220 V potential difference. If they are connected in parallel, how much current will flow in the main conductor?
Name the factors on which the heat produced in a wire depends when current is passed in it, and state how does it depend on the factors stated by you.
Name any six domestic appliances based on the heating effect of electric current.
Answer the following question:
what is the heating effect of the electric current? state any four applications of it?
Write scientific reason.
A coil made up of alloy Nichrome is used in the electric heater cooker as a resistor.
How can overloading be avoided?
Mark the correct choice
- Assertion: Electric appliances with a metallic body have three wire connections.
- Reason: Three-pin connections reduce the heating of the connecting wires.
A fuse wire repeatedly gets burnt when used with a good heater. It is advised to use a fuse wire of:
Name two electric devices for each where
- heating effect of current is used and
- magnetic effect of current is used.
Match the following
| 1. | Bulb | a. | Conductor |
| 2. | Electroplating | b. |
Insulator |
| 3. | Pure water | c. | Heating effect of current |
| 4. | Salt solution | d. | Chemical effect of current |
The following is not a safety device.
An electrochemical cell converts ______ energy into ______ energy.
Write an expression for the amount of heat produced in a resistor when an electric current is passed through it stating the meanings of the symbols used.
When a current I flows through a wire of resistance R for time t then the electrical energy produced is given by ______.
