Advertisements
Advertisements
Question
Why do we cover plug pin holes which are within the reach of children with cellotape or a plastic cover when not in use?
Advertisements
Solution
The child may put his/her fingers into the socket and he/she may get an electric shock which could be fatal. Plastic/cellotape is a bad conductor of electricity and hence chances of electric shock get reduced.
APPEARS IN
RELATED QUESTIONS
An electric bell has an electromagnet.
Which effect of current can be utilised in detecting a current carrying wire concealed in a wall?
When the switch S is closed in the figure given below, the pointer of the galvanometer moves to the right.
If S is kept closed, will the pointer:
(a) return to zero?
(b) stay over on the right?
(c) move to the left and stay there
(d) move to and fro until S is opened
What is the function of a split ring in an electric motor?
Answer the following question:
State the effect on the magnetic needle in Oersted’s experiment when:
(a) the current is passed through the wire.
(b) the current through the wire is increased
(c) the current through the wire is reversed.
A wire with green insulation is usually the live wire of an electric supply.
The figure given below shows the magnetic field around the conductor. Study it and answer the questions:

- What changes are caused by increasing current?
- What do you see when the magnetic needle is kept a little away from the wire?
- In the second part of the figure, the iron filings arrange themselves in a circular manner around the wire. Why does this happen?
A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic field. He took a small aluminium rod AB, a strong horse shoe magnet, some connecting wires, a battery and a switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of this phenomenon, answer the following questions:

- Why does the rod get displaced on passing current through it?
- State the rule that determines the direction of the force on the conductor AB.
-
- If the U-shaped magnet is held vertically and the aluminium rod is suspended horizontally with its end B towards due north, then on passing current through the rod from B to A as shown, in which direction will the rod be displaced?
- Name any two devices that use current carrying conductors and magnetic fields.
OR
Draw the pattern of magnetic field lines produced around a current carrying straight conductor held vertically on a horizontal cardboard. Indicate the direction of the field lines as well as the direction of current flowing through the conductor.
Using an electromagnet, you can make a working model of a railway signal as shown in figure.

Make four electromagnets with 20, 40, 60 and 80 turns. Connect them one by one to a battery of 2 cells. Bring the electromagnet near a box of pins. Count the number of pins attracted by it. Compare the strengths of the electromagnets.
