Class 10 , chapter- 7 (SCIENCE)
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CLASS NOT ES
1. Why does a magnet exert force on another magnet when the two magnets are not in
contact? - answerThe magnetic field from north to south increases when they're closer
together, and when they repel the repelling force increases as well. This is all due to the
magnetic field.
3. Describe how a compass needle moves when it is placed in a magnetic field. -
answerThe needles always line up with the magnetic lines going from North to South in
the magnetic field.
4. Explain why only certain materials are magnetic. - answerThe reason certain
materials are magnetized and some are not is because certain materials' electrons
cancel out, resulting in the non magnetization of the specific object.
5. Explain how heating a bar magnet would change its magnetic field. - answerThe
action of heating a magnet will cause the atoms to vibrate, thus weakening the magnetic
field.
8. Explain what happens when a magnet is placed near a current-carrying wire. -
answerThe magnet will push the wire away from the magnet due to the force exerted,
the Lorentz force (unless the angle between the flow of current and magnetic lines is
0°).
9. A bar magnet is repelled when an electromagnet is brought close to it. Describe how
the bar magnet would have moved if the current in the electromagnet had been
reversed. - answerThe bar magnet would be attracted to the electromagnet because the
pole would be the opposite.
10. Define the term electromagnetic force. Give an example of a machine that uses this
force. - answerElectromagnetic force is defined in the textbook as, "the attractive or
repulsive force between electric charges and magnets". An example of a machine that
uses this force is a tape recorder.
18. Explain why a magnet sitting next to a wire does not induce a current in the wire. -
answerA change in the magnetic field of a coil of wire will cause a voltage to be induced
in the coil. If the magnet sitting next to the wire does not move, there is no electric
current in the wire.
