In a battery charger (ex.laptop charger), the ac voltage of 120volts is converted to a DC voltage to charge the batteries in the laptop. But, the maximum current available from a 120v socket is 15 amps, whereas some chargers at the output provide 30 amps at 12 Volts DC. How is this possible ?
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1\$\begingroup\$ conservation of energy: Pin = Pout. \$\endgroup\$– user16222Commented Jul 26, 2015 at 16:30
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The power from 120 V * 15 A is 1800 W, if you use a transformer, you can get the same power from any voltage, 12 volts * 30 A is only 360 Watts
A transformer converts the voltage down from 120 V to 12 V, but power is conserved (not 100%, but good enough). So when 120 volts is transformed down to 12 volts, it can output 10 times the current on the 12 volt side. And it will still be the same voltage-current product.
