You are measuring the current in a circuit that is operated on an 18 V battery. The ammeter reads 40 mA. Later you notice the current has dropped to 20 mA. How much has the voltage changed?
A.9 V
B.900 mV
C.0 V
D.18 V
A.9 V
B.900 mV
C.0 V
D.18 V