# How is potential difference from power station transmitted to the primary coil of a transformer?

I am confused because i am not sure what does a powerstation transmit and the notes mentioned something about transmission of potential difference. Since the potential difference at the primary coil in a step down transformer is high why does it have a low current and vice versa at the secondary coil as i thought high potential difference results in high current but i get the part that power should be a constant at both sides of the transformer

At the power station, the output of the generator is connected to the step-up transformer primary. this maximizes the voltage and minimizes the current- which minimizes the power losses in the transmission line.

At the other end of the transmission line, a step-down transformer primary is connected to the power line and its secondary is connected to the local power distribution system. This transformer brings the voltage back down and raises the current back up again.

The two things to remember are this: 1) transformers conserve power (power in = power out) which means if a transformer kicks up the voltage it also kicks down the current at the same time, and 2) power = voltage x current no matter what.

• But doesn't a voltage result in a current so why is there not much current at the primary side even though the voltage is high – Toh Jia Han Apr 30 at 5:45
• think of a transformer as if it were the transmission in your car. the turns ratio is like the gear ratio. when starting off, you need lots of torque and only a little RPM. When cruising down the road, you need only a little torque but more RPM. – niels nielsen Apr 30 at 6:08
• is it possible to use another example because im just a student who haven't even learnt about torque and know nothing about cars :/ – Toh Jia Han Apr 30 at 13:51

i thought high potential difference results in high current

All other things being equal, you're correct. For a circuit with a resistive load, higher voltage (higher potential difference) does mean a higher current.

If the power station were to increase the voltage it supplies slightly, the current in both sides would increase. It's just that the ratio of the currents will be constant.

You can think of the transformer like a lever. We want to lift a rock. A lever lets us use less force to lift it, but it means we need to move our lever at a higher speed than the rock. The ratio between the forces on both side (and the speed of both sides) is constant.