Transcript Do now!
Do now! When do you want the test?! Today’s lesson - Transformers Can you gather around Mr Porter? Transformers A changing current in the primary coil produces a changing magnetic field in the coil. This changing magnetic field induces a changing current in the secondary coil. Changing voltages The ratio of the number of turns on the coils equals the ratio of the voltages # of turns = Np # of turns = Ns Vp/Vs = Np/Ns Changing voltages A transformer where the voltage rises is called a step-up transformer Changing voltages A transformer where the voltage falls is called a step-down transformer No energy for nothing Power in = power out VpIp = VsIs a.c. only Because transformers rely on induction (changing fields), they only work with alternating current (a.c.) Why do we need transformers? Current flowing through wires causes them to get hot and energy is lost. Why do we need transformers? Keeping the current low means electricity can be transported long distances without losing too much energy. Why do we need transformers? However, in order to send a large quantity of energy, high voltages are needed. Transmission of Electricity Step-up Step-down Today’s lesson Practice questions for this topic Deciding when to have the test!