A transformer supplies the motors in a pump house at a water-treatment works. Its primary coil is connected to an alternating supply at 11 000 V11\,000\ \text{V}11000 V and its secondary potential difference is 400 V.
The motors draw a total secondary current of 330 A.
Assume that the transformer is 100% efficient.
Calculate the current in the primary coil.
Use the equation
VP×IP=VS×ISV_P \times I_P = V_S \times I_SVP×IP=VS×IS
There are 5500 turns on the primary coil.
Calculate the number of turns on the secondary coil.
Use the equation
VPVS=NPNS\displaystyle \frac{V_P}{V_S} = \frac{N_P}{N_S}VSVP=NSNP
The pump house is a long distance from the entrance to the site. Engineers place the transformer beside the pump house rather than beside the site entrance.
Explain why this position reduces the energy wasted in the connecting cables.
108 exam-style questions on Edexcel GCSE Physics 13.2 Transformers and the National Grid, covering 13.2.1 Transformers and induction, 13.2.2 The transformer turns-ratio equation, 13.2.3 The National Grid, 13.2.4 The transformer power equation, and 13.2.5 Advantages of high-voltage transmission. Each one has a worked solution and a mark scheme showing where the marks go.