A voltmeter reads the voltage across a component. First, recall how it connects:
To measure the voltage across a motor, how is the voltmeter connected?
In a parallel circuit, predicting any branch voltmeter's reading takes one step. Here is a 9.0 V supply driving two resistors, R1 and R2, on parallel branches, with a voltmeter across R2.
Every branch of a parallel circuit has the full source voltage across it. R2's branch therefore has the full 9.0 V across it. The voltmeter reads 9.0 V.
Now the voltmeter is moved across R1 instead. That branch also has the full 9.0 V across it, so the reading is again 9.0 V.
Careful with the trap: the reading does not halve because there are two branches, and it does not depend on the branch's resistance.
A 15 V supply drives a lamp and a fan in parallel. What does a voltmeter across the fan read?
The fan sits on a parallel branch, so it has the full source voltage across it.
The source voltage is 15 V.
The voltmeter across the fan reads 15 V.
A third branch holding a buzzer is added to the same 15 V circuit. What does a voltmeter across the buzzer read?
The buzzer's branch also runs from one supply terminal to the other.
Every branch has the full source voltage across it, however many branches there are.
The voltmeter across the buzzer reads 15 V.
Six in a row now. One step each.
A 12 V supply drives two parallel resistors. What is the voltage across each, in V?
Two heaters sit in parallel across a 240 V supply. Voltage across either heater, in V?
A fan and pump run in parallel across 36 V. The pump's voltage, in V?
A buzzer and LED share a 7.5 V battery in parallel. The LED's voltage, in V?
Three motors share a 48 V supply in parallel. Voltage across each motor, in V?
Two parallel speakers share an 18 V battery. A voltmeter across one reads, in V?
A 4.5 V battery drives a doorbell and a lamp in parallel. What does a voltmeter across the doorbell read?
Voltmeters sit across both branches of a parallel circuit with a 60 V source. What do they read?
A voltmeter across one branch of a parallel pair reads 24 V. What does a voltmeter across the other branch read?