Magnets and magnetic fieldsIB MYP Physics: Subtopic test

1. 1
   A student in Mumbai tests a bar magnet with four objects: an iron nail, a copper coin, a steel paper clip and a plastic ruler.

   (a)

   Which objects will the bar magnet attract?

   [1 mark]

   • AThe copper coin and the plastic ruler
   • BThe iron nail and the steel paper clip
   • CThe iron nail and the copper coin
   • DAll four objects

   (b)

   The student holds the north pole of a second bar magnet close to the north pole of the first bar magnet. What happens?

   [1 mark]

   • AThey attract each other
   • BNothing happens because magnets only affect iron
   • CBoth magnets lose their magnetism
   • DThey repel each other

   (c)

   The iron nail sticks to the magnet but falls off when the magnet is removed. Explain what is meant by an induced magnet.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A hiker in the Swiss mountains uses a compass to find her way. The compass needle is a small bar magnet that is free to turn.

   (a)

   Why does the compass needle point towards the north?

   [1 mark]

   • AThe Earth has a magnetic field and the needle lines up with it
   • BGravity pulls the needle towards the north
   • CThe Sun attracts the needle
   • DThe wind in the atmosphere pushes the needle

   (b)

   The hiker places her compass near a bar magnet. In which direction do the magnetic field lines point outside the bar magnet?

   [1 mark]

   • AFrom the south pole to the north pole
   • BIn closed circles around the middle of the magnet
   • CFrom the north pole to the south pole
   • DStraight out from the north pole and never come back

   (c)

   Describe how the hiker could plot the magnetic field around a bar magnet using a small plotting compass.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A mechanic in Dubai wants to turn a steel screwdriver into a magnet so that it can pick up small steel screws. She has a strong bar magnet and a hammer.

   (a)

   Describe how she can magnetise the steel screwdriver using the bar magnet.

   [3 marks]

   (b)

   Describe two ways of demagnetising the screwdriver, and explain why iron would not be a good choice for a screwdriver that must stay magnetic.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A recycling plant in Rotterdam separates steel food cans from aluminium cans and plastic bottles. A student team models the process by testing how close a bar magnet must be to a steel paper clip to attract it. The plant manager is also considering whether to sort the waste with magnets or to employ more workers to sort it by hand.

   (a)

   The team hypothesises that the distance between the magnet and a steel paper clip affects whether the magnet can attract it. State a testable hypothesis with a scientific reason, identify the independent, dependent and one control variable, and outline a safe method.

   [6 marks]

   (b)

   Discuss and evaluate whether the plant should sort its waste with magnets rather than by hand.

   [6 marks]

   Total for question 4: 12 marks

End of questions