A stepdown transformer is used for recharging the batteries of portable devices such as tape players. the turns ratio inside the transformer is 13:1 and it is used with 120 V rms household service. if a particular ideal transformer draws 0.350 A from the house outlet, what are the voltage and the current supplied to a tape player from the transformer. How much power is delivered?
The tape player receives an output of 120/139.2V rms from the transformer. The tape player's current draw on the transformer is 2.6mA or 0.026A. Your power usage is 10.04Wh or .01kWh.
I'm not going to do your homework for you, but here is how to set up the problem. Given: Input Voltage 120 V Input Current 0.350 A Turns Ratio 13:1 For an ideal transformer, VA(in) VA(out) Transformer turns ratio can be computed as V(in) ÷ V(out). Use algebra to solve for Output voltage. Output Voltage Input Voltage ÷ Turns Ratio The turns ratio can also be computed as I(out) ÷ I(in). Again, use algebra to solve for the outut current I(out) Output Current Input Current x Turns Ratio This is an AC power problem, so we have to either assume unity power factor, or label our power calculations as apparent power (VA). Apparent Power Voltage x Current As an ideal transformer, you can calculate the power on either the input or output side of the transformer. If you get different numbers, you did something wrong. Power V(in) x I(in) Power V(out) x I(out)
