**Q4: **

Which of the following is a suitable material for the core of a transformer?

- AAluminum
- BCopper
- CPolypropylene (plastic)
- DIron
- ECarbon

**Q5: **

A transformer has 200 turns on its primary coil and 50 turns on its secondary coil. If the input potential difference is 20 V, what is the output potential difference?

**Q6: **

What kind of current are transformers used with?

- ABoth alternating current and direct current
- BDirect current
- CAlternating current

**Q7: **

A step-up transformer has turns on its secondary coil than on its primary coil, and, thus, a potential difference across the secondary coil than across the primary coil.

- Afewer, higher
- Bmore, lower
- Cfewer, lower
- Dmore, higher

**Q8: **

A 100% efficient transformer has 5 times as many turns on its secondary coil as it does on its primary. If the current through the primary coil is 20 A, what is the current through the secondary coil?

**Q9: **

A step-up transformer needs to change the potential difference of an alternating current from 50 V to 250 V. If the transformer has 100 turns on its primary coil, how many turns does it need to have on its secondary coil?

- A100 turns
- B250 turns
- C50 turns
- D500 turns
- E125 turns

**Q10: **

A step-up transformer has 8 times as many turns on its secondary coil as it does on its primary coil. If its input potential difference is 40 V, what is its output potential difference?

**Q11: **

Which of the following electrical properties are changed by a efficient transformer?

- ACurrent only
- BPotential difference only
- CPower only
- DBoth potential difference and current
- EPotential difference and power

**Q12: **

A step-down transformer changes the potential difference of an alternating current from V to 250 V. If it has 25 turns on its secondary coil, how many turns does it have on its primary coil?

- A400 turns
- B40 turns
- C100 turns
- D turns
- E250 turns