Group 1
1. Which statement is always true for an electromagnet?
A. It attracts steel objects.
B. It remains magnetic forever.
C. It works only when current flows through it.
D. It has only one pole.
C. It works only when current flows through it.
1. When current through a coil is stopped, the magnetic field around it
A. increases gradually
B. changes direction
C. disappears
D. becomes temporary
C. disappears
1. Which device uses the magnetic effect of electric current?
A. Electric iron
B. Electric stove
C. Water heater
D. Lifting electromagnet
D.Lifting electromagnet
1. Why is an iron nail inserted inside a current-carrying coil?
A. To reduce current
B. To strengthen the magnetic effect
C. To stop heating
D. To reverse polarity
B. To strengthen the magnetic effect
1. In a lifting electromagnet, iron objects are released when
A. the number of turns increases
B. the iron core melts
C. current is switched OFF
D. the crane moves upward
C. current is switched OFF
2. A student replaces one cell with two cells while keeping everything else unchanged. Which change is expected?
A. Weaker magnetic field
B. Stronger magnetic field
C. No magnetic field
D. Coil becomes permanent magnet
B. Stronger magnetic field
2. A current-carrying coil without an iron core can still
A. behave like a magnet
B. become a permanent magnet
C. loses magnetic property
D. attract metal clips
A. behave like a magnet
2. A crane operator wants to release heavy iron scraps instantly. Which property of an electromagnet makes this possible?
A. Permanent polarity
B. Magnetic field disappears when current stops
C. Iron core melts quickly
D. Heating effect of current
B. Magnetic field disappears when current stops
2. Which change will NOT affect the strength of an electromagnet?
A. Increasing the number of turns
B. Increasing the current through the coil
C. Inserting an iron core
D. Reversing the direction of current
D. Reversing the direction of current
2. Which change will definitely make an electromagnet stronger?
A. Reversing the direction of current through the coil
B. Increasing the number of turns of the coil
C. Changing the North pole into the South pole
D. Removing the iron core and using a thicker wire
B. Increasing the number of turns of the coil
3. Four students make electromagnets. Which one is expected to be strongest?
A. 20 turns, two cells, no iron core
B. 50 turns, one cell, iron core
C. 20 turns, two cells, iron core
D. 50 turns, two cells, iron core
D. 50 turns, two cells, iron core
2. A compass near a coil deflects eastward. After reversing the battery terminals, the needle will most likely
A. stop deflecting.
B. deflect westward.
C. show greater deflection.
D. return to its original direction.
B. deflect westward.
3. If a magnetic compass placed near a wire shows no deflection, which conclusion is definitely correct?
A. The magnetic field is absent or negligible.
B. The current direction has reversed.
C. The wire has fewer turns.
D. The iron core has been removed.c
A. The magnetic field is absent or negligible.
3. Which factor is responsible for the deflection of a compass needle near a wire?
A. Heating effect of current
B. Magnetic field produced by current
C. Chemical effect of current
D. Presence of an iron core
B. Magnetic field produced by current
3. A current-carrying coil attracts paper clips. If the direction of current is reversed, what will happen to the paper clips?
A. They will immediately fall.
B. They will still remain attracted.
C. The coil will stop behaving like a magnet.
D. The iron core will lose its magnetism.
B. They will still remain attracted.
4. A coil connected to a battery attracts 8 paper clips. Without changing the coil, the battery is replaced by one having more cells. What is most likely to happen?
A. Poles of the electromagnet reverse.
B. Compass deflection decreases.
C. The electromagnet attracts more clips.
D. The coil behaves like a permanent magnet.
C. The electromagnet attracts more clips
4. A student removes the iron core from an electromagnet while current continues to flow. What will happen?
A. The magnetic field disappears completely.
B. The electromagnet becomes weaker.
C. The polarity reverses.
D. The number of poles reduces to one.
B. The electromagnet becomes weaker.
4. Which statement explains why cranes use electromagnets instead of permanent magnets?
A. Their polarity can be reversed.
B. They can be switched ON and OFF.
C. They attract more materials.
D. Their strength depends only on current.
B. They can be switched ON and OFF.
4. An electromagnet is attracting paper clips. Which change is least likely to make the clips fall immediately?
A. Disconnecting the battery.
B. Removing the iron core.
C. Reversing the direction of current.
D. Breaking the circuit
C. Reversing the direction of current.
4. Which observation proves that the magnetic field around a current-carrying wire has changed direction?
A. The wire becomes hotter.
B. The compass needle deflects to the opposite side.
C. More paper clips are attracted.
D. The iron core becomes stronger.
B. The compass needle deflects to the opposite side
5. A lifting electromagnet is switched ON and lifts iron scrap. After some time, the wire becomes warm, but the scrap suddenly falls. Which explanation is most reasonable?
A. Current became insufficient due to battery weakening.
B. The iron core lost its magnetism permanently.
C. Reversal of current changed the poles.
D. Increase in heating effect destroyed the magnetic field.
A. Current became insufficient due to battery weakening
5. A student observes that reversing the battery terminals does not cause paper clips to fall from an electromagnet. Which conclusion is best?
A. Reversing current changes polarity but not the ability to attract magnetic materials.
B. Reversing current increases the magnetic strength.
C. Reversing current makes the iron core permanent.
D. Reversing current removes one magnetic pole.
A. Reversing current changes polarity but not the ability to attract magnetic materials.
5. Which observation provides the strongest evidence that a current-carrying coil behaves like a bar magnet?
A. The wire becomes warm.
B. The coil attracts iron pins and possesses two poles.
C. The battery voltage decreases.
D. The iron core becomes hot.
B. The coil attracts iron pins and possesses two poles.
5. A student says, "Removing the iron core from an electromagnet will make the North pole become the South pole." Which statement is correct?
A. The student is correct because the iron core determines polarity.
B. The student is incorrect because removing the iron core mainly reduces strength, not polarity.
C. The student is correct because the current direction changes automatically.
D. The student is incorrect because the coil loses all magnetic properties
B. The student is incorrect because removing the iron core mainly reduces strength, not polarity.
5. Which factor distinguishes a lifting electromagnet from a permanent magnet most effectively?
A. Presence of North and South poles.
B. Ability to attract iron objects.
C. Dependence of magnetic action on electric current.
D. Existence of a magnetic field.
C. Dependence of magnetic action on electric current.