Question

1. when measuring across a resistor, ____ and ____ are always in phase

a resistance and voltage
b voltage and current
c resistance and current
d all of the above

Explanation:

In a resistor - only AC circuit, according to Ohm's law \(V = IR\). The voltage \(v = V_m\sin(\omega t)\) and current \(i=I_m\sin(\omega t)\) (where \(V_m = I_mR\)). The phase angle \(\varphi=\theta_v-\theta_i = 0\) (since \(\theta_v\) and \(\theta_i\) are the phase angles of voltage and current respectively). Resistance is a property of the resistor (a constant for a given resistor at a given temperature, not a phasor quantity that can be in - phase with voltage or current in the AC phasor sense).

Answer:

B. voltage and current