A space heater's wire carries a current of 4 A. Enter the charge, in coulombs, that passes a point in the wire each second.
How large is the current through a lamp? You cannot see charge passing. An instrument can count it for you. But where you connect that instrument decides whether its reading means anything.
In earlier grades you saw two ways to connect components: one after another along a single path (in series), or side by side on separate paths (in parallel). Reading a current needs the first way.
The current through the lamp is the charge passing through it each second.
An instrument that reads that flow is called an ammeter. On a diagram, the ammeter is drawn as a circle marked A.
To read the lamp's current, the ammeter must carry the same flow that passes through the lamp.
So the ammeter is connected in series with the lamp: wired into the same single path.
Wired like this, every coulomb that passes through the lamp also passes through the ammeter. The ammeter reads the lamp's current.
To measure the current through a motor, how is the ammeter connected?
Now the wrong hookup. Wired in parallel, on a side path beside the lamp, the ammeter does not carry the lamp's flow.
On a side path, current detours through the ammeter instead of the lamp.
So a parallel-wired ammeter changes the circuit, and its reading is not the lamp's current.
A technician wants the current through a small pump motor. Where does the ammeter go?
Write down the rule:
An ammeter reads the current through a point, and it must be connected in series at that point.
Apply it:
In series with the motor, the whole flow through the motor also passes through the ammeter.
The ammeter is wired in series with the motor, in the motor's own path.
An ammeter is wired into the same single path as a buzzer. What does the ammeter read?
An ammeter is wired in series with a buzzer, and the ammeter reads 0.2 A. What does that 0.2 A state?
Write down the rule:
In series, the ammeter carries the same flow as the buzzer.
Read the number:
Its reading is the buzzer's current: the charge passing through the buzzer each second.
0.2 A is the current through the buzzer: 0.2 C passing through it each second.
Leah wires an ammeter on a side path beside a lamp instead of into the lamp's path. Why is her reading not the lamp's current?
A box fan's motor current must be measured. Which wiring is correct?
An ammeter wired in series with a heater element reads 3 A. What is that 3 A?
Noah clips an ammeter's two leads to the two ends of a toy car's motor, making a side path beside it. What happens?