Advertisements
Advertisements
प्रश्न
How does the resistance of a wire vary with its area of cross-section?
Advertisements
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
Name any two effects of electric current.
The elements of electrical heating devices are usually made of:
(a) tungsten
(b) bronze
(c) nichrome
(d) argon
Three heaters each rated 250 W, 100 V are connected in parallel to a 100 V supply. Calculate:
- the total current taken from the supply
- the resistance of each heater and
- the energy supplied in kWh to the three heaters in 5 hours.
Give Scientific reason
In the electric equipment producing heat e.g. iron, electric heater, boiler, toaster etc, an alloy such as Nichrome is used, not pure metals.
Give Scientific reason.
In practice, the unit kWh is used for the measurement of electrical energy, rather than joule.
Identify the figure and give its use.
Find the odd one out and give its explanation.
What is a short circuit?
Name any two appliances which works on the phenomenon of heating effect of electric current.
What does overloading cause?
How can overloading be avoided?
Name any two appliances which work under the principle of heating effect of current.
An electric iron consumes energy at the rate of 420 W when heating is at the maximum rate and 180 W when heating is at the minimum rate. The applied voltage is 220 V. What is the current in each case?
Why is parallel arrangement used in domestic wiring?
______ wire is used in the filament of the bulbs.
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 |
Two students decided to investigate the effect of water and air on iron object under identical experimental conditions. They measured the mass of each object before placing it partially immersed in 10 ml of water. After a few days, the object were removed, dried and their masses were measured. The table shows their results.
| Student | Object | Mass of Object before Rusting in g |
Mass of the coated object in g |
| A | Nail | 3.0 | 3.15 |
| B | Thin plate | 6.0 | 6.33 |
What might be the reason for the varied observations of the two students?
An electric kettle consumes 1 kW of electric power when operated at 220 V. A fuse wire of what rating must be used for it?
