Associated Builders And Contractors (ABC) Year 1 Practice Test

Energy storage in a capacitor is in the electric field created between its plates. The false statement claims energy is stored in a magnetic field, which is not how capacitors work—magnetic fields are tied to current in inductors or coils, not to the energy storage mechanism of a capacitor. The electric field between the plates stores energy, quantified by (1/2) C V^2 or (1/2) QV, which is why capacitors can release energy when connected to a circuit load. When a capacitor is connected through a conductive path, charge flows and the stored energy is discharged through that path, delivering current to the circuit. In AC, a capacitor presents capacitive reactance, Xc = 1/(2πfC), causing the current to lead the voltage due to the time-dependent charging and discharging. So, the statement about storing energy in a magnetic field is the one that doesn’t fit the behavior of capacitors.