Series current: the same at every point

Are the lamp and the resistor connected in series or in parallel?

Three ammeters sit around one series loop: one beside the battery, one between the two bulbs, one after the second bulb. Which ammeter reads the most?

One loop: a 6 V battery, two bulbs, and ammeters at three points. No readings yet.

Here are the readings. A1, beside the battery, reads 0.5 A. A2, between the two bulbs, also reads 0.5 A. And A3, after the second bulb, also reads 0.5 A.

All three ammeters agree: 0.5 A at every point on the loop.

This circuit is one loop with no junctions, so the current is the same at every point: 0.5 A.

Now the second bulb is swapped for a resistor. The three ammeters read 0.3 A, 0.3 A, and 0.3 A.

One bulb swapped for a resistor: the ammeters still agree, now at 0.3 A.

This circuit is one loop with no junctions, so the current is the same at every point: 0.3 A.

In a series circuit, the current is the same at every point around the loop.

The current does not shrink along the way: the bulb after the battery carries exactly the same current as the bulb farther around the loop.

Ammeter P reads 0.6 A. Ammeter Q sits later around the same series loop. How does Q's reading compare with P's?

Two identical bulbs sit in one series loop. Dani says the bulb nearer the battery glows brighter, because the current reaches it first. Is Dani correct?

One circuit near the boundary. This one has a junction where the wire splits into two paths, so the current is not the same at every point. The same-current rule is for series circuits: one loop, no junctions.

A junction splits the wire into two paths: the same-current rule does not apply here.

Two ammeters sit at different points around one series loop. The first reads 0.6 A. Is the second reading bigger, smaller, or the same?

Write down the rule:

In a series circuit, the current is the same at every point around the loop.

Apply it:

Both ammeters sit on the same single loop, so both read the same current.

The second reading is the same: 0.6 A.

In a series loop, how does the current returning to the battery compare with the current that left it?

Your turn

A series circuit has a battery, a resistor, then a bulb. An ammeter before the resistor reads 0.8 A. What does an ammeter placed after the bulb read?

A series loop contains a battery and three bulbs. Which statement about the current in the loop is correct?

A series loop has a battery, a closed switch, and two resistors of different sizes. An ammeter between the two resistors reads 0.35 A. What does an ammeter between the battery and the switch read?