Advertisements
Advertisements
Question
How does the resistance of a wire vary with its:
diameter?
Advertisements
Solution
We know that the area of cross-section, A = πr2 = π (d / 2)2, where r is the radius and d is the diameter of the wire. So on increasing the diameter of the wire, its resistance decreases.
APPEARS IN
RELATED QUESTIONS
What is nichrome? State its one use.
An electric iron of resistance 20 ohms draws a current of 5 amperes. Calculate the heat produced in 30 seconds.
What is meant by the heating effect of current?
Name the material which is used for making the filaments of an electric bulb.
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 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
Give Scientific reasons.
In the electric equipment producing heat e.g. iron, electric heater, boiler, toaster etc, an alloy such as Nichrome is used, not pure metals.
What is a short circuit?
What does overloading cause?
Define fuse.
Name some devices that run using heat effect of electric current
Explain the heating effect of electric current.
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:
An electric fuse is a wire made up of a material having ______ melting point.
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?
In which of the following applications of Iron, rusting will occur most? Support your answer with valid reason.
| A | B | C | D |
 |
 |
 |
 |
An electric kettle of 2 kW is used for 2h. Calculate the energy consumed in
- kilowatt hour and
- joules.
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.
An electric iron of resistance 20 Ω draws a current of 5 A. The heat developed in the iron in 30 seconds is ______.
