A Answer the following in not more than 20 words.
1. What do you need to apply across a bulb to cause a current to flow through it?
2. Why does a bulb get warmer than the wires that connect it to a battery?
3. A magnetic needle gets deflected when brought near a current-carrying conductor. What does this show?
4. What happens when you place an iron nail in a current-carrying coil?
5. Why do we use a soft iron core in an electromagnet?
6. Name four devices that use the heating effect of electric current
7. Mention four applications of electromagnets.
Answers
Answer:
Answer 6. 1. Electric kettle
2. Electric bulb
3. Electric toaster
4. Electric oven
Answer 7. 1. in banking card
2. in removing iron from scrap yard
3. in speakers
4. in t.v. to display
Answer 5. Soft iron is generally used for making electromagnets because it has high magnetic permeability, i.e it can easily gain magnetic properties when current is passed around the core and quickly lose when current is stopped.
Answer 4. When the iron strip is in contact with the screw, the current flows through the coil which becomes an electromagnet. It then, pulls the iron strip. In the process, the hammer at the end of the strip strikes the gong of the bell to produce a sound.
Answer 3. magnetic needle gets deflected when it is brought near. a current carrying conductor. it shows that the the current carrying conductor is a good conductor of electricity.
Answer 2. Bulb contains a filament which is made up of tungsten. Tungsten has high resistivity, greater than that of the copper which makes up the wires. Hence the bulb gets warmer as compared to the wire.
Answer 1. We need to apply voltage across a bulb to cause a current to flow through it.