A step-up transformer has 500 turns on the primary and 10,000 turns on the secondary. The input voltage is 230 V. (a) Calculate the output voltage. (b) If the primary current is 8 A, calculate the secondary current (assuming ideal transformer). (3 marks)
Hint: (a) Turns ratio: Vs = Vp × (Ns/Np). (b) Power in = Power out: VpIp = VsIs. Solve for Is.
+30 XP
1 markWhy high voltage transmissionAQA 8463 style
Transmitting electricity at high voltage reduces energy losses. Why?
A Higher voltage means lower resistance in the cables
B Higher voltage allows higher current, which is more efficient
C For a given power, higher voltage means lower current, and power loss in cables = I²R — lower current means much less power wasted
D High-voltage cables have thicker insulation which prevents heat loss
3 marksWhy AC for transformersAQA 8463 style
Explain why transformers only work with alternating current (AC) and not direct current (DC). (3 marks)
Hint: Key concept: electromagnetic induction requires a CHANGING magnetic field. AC gives changing current → changing field. DC gives constant current → constant field → no induction.
+30 XP
1 markTransformer direction — inversion trapAQA 8463 Paper 1 style ⚡ Common error
A student writes: "A step-up transformer increases the current in the transmission cables." Which of the following correctly identifies the error and gives the right answer?
A The student is correct — step-up transformers increase current.
B The student meant voltage, not current — step-up increases voltage.
C The student is wrong. Step-up transformers increase voltage and decrease current — the opposite of what was stated.
D The student is wrong, but step-up transformers also decrease resistance, not current.
2 marksTransformer gap-fill — paper formatAQA 8463 style — same format as exam
Complete the sentences. A step-up transformer increases the ___ and decreases the ___. A step-down transformer decreases the ___. Using transformers decreases the ___ transfer from the overhead cables. (2 marks)
Words to choose from: charge, current, energy, potential difference, resistance. Each may be used once or not at all.