Question 1
A student wants to measure both the current through a lamp and the voltage across it. Which statement correctly describes how to connect the measuring instruments?No clue? Show me the answer
Correct answerCorrect!
IncorrectStep-by-step walkthrough
Choose a solution method
Method #1Direct ApproachStep 1: Recall the rules for ammeters
An ammeter measures current. Current must flow through it, so it must be placed in series with the component. Ammeters have very low resistance so they don't affect the circuit.
Step 2: Recall the rules for voltmeters
A voltmeter measures potential difference (voltage) across a component. It must be connected in parallel with the component. Voltmeters have very high resistance so minimal current flows through them.
Step 3: State the correct connection
The correct setup is: ammeter in series with the lamp, voltmeter in parallel with the lamp.
Method #2Process of EliminationStep 1: Identify what is being asked
We need to identify the correct placement of an ammeter and a voltmeter to measure current through and voltage across a lamp.
Step 2: Eliminate 'both in series'
Both in series is wrong. A voltmeter has very high resistance — placing it in series would block almost all current and the lamp would not light.
Step 3: Eliminate 'ammeter in parallel, voltmeter in series'
This is backwards. An ammeter in parallel creates a near short-circuit (its very low resistance would divert all current away from the lamp), potentially damaging the ammeter.
Step 4: Eliminate 'both in parallel'
Both in parallel is wrong. The ammeter must be in series to measure the current flowing through the lamp, not just the voltage across it.
Step 5: Select the correct answer
Ammeter in series, voltmeter in parallel is correct. This is the standard method for measuring current through and voltage across any component.
5 more questions in this topic
Pick this up in your Library: it holds the whole topic, notes, cheatsheet and questions. Your answers here are kept on this device.