Electricity and Magnetism Practise guide

Electricity and Magnetism Practise guide 1) An ac source of period T and maximum voltage V is connected to a single unknown ideal element that is either a resistor, and inductor, or a capacitor. At time t = 0 the voltage is zero. At time t = T/4 the current in the unknown element is equal to zero, and at time t = T/2 the current is I = -Imax, where Imax is the current amplitude. What is the unknown element? A) a resistor B) an inductor C) a capacitor D) an inductor or a capacitor Answer: C 2) When an LRC series circuit is driven at resonance, which of the following statements about the circuit are correct? (There may be more than one correct choice.) A) The impedance of the circuit is zero. B) The impedance of the circuit has its maximum value. C) The impedance of the circuit has its minimum value. D) The inductive reactance and the capacitive reactance are both zero. E) The inductive reactance and the capacitive reactance are exactly equal to each other. Answer: C, E 3) If the magnetic field of an electromagnetic wave is in the +x-direction and the electric field of the wave is in the +y- direction, the wave is traveling in the A) xy-plane. B) +z- direction. C) -z- direction. D) -x-direction. E) -y- direction. Answer: C