EI · 8 cards

Series Circuits flashcards

8 cards with the formulas, rules and traps from this lesson. Answer in your head, then flip to check.

Rule · 1/8
In a series circuit, how does current compare from one resistor to the next?
It is identical everywhere: $I_{T} = I_{1} = I_{2} = I_{3}$ . There is only one path, so resistors lower voltage, never the current passing through them.
Formula · 2/8
How do you find total resistance of resistors in series?
Add them: $R_{T} = R_{1} + R_{2} + R_{3} + \dots$ (ohms). The total is always larger than the largest single resistor, e.g. 10, 22 and 68 $Ω$ give 100 $Ω$ .
Rule · 3/8
What does Kirchhoff's voltage law say about a single series loop?
The drops add up to the source voltage: $V_{S} = V_{1} + V_{2} + V_{3}$ , i.e. $V_{S} - V_{1} - V_{2} - V_{3} = 0$ . A missing drop is the source minus the known drops.
Formula · 4/8
Voltage-divider formula: drop across one series resistor without finding current?
$V_{n} = V_{S} \times \frac{R _{n}}{R _{T}}$ . The drop is the source voltage times that resistor's share of total resistance; 15 V on 10 $Ω$ + 20 $Ω$ puts 10 V on the 20 $Ω$ .
Fact · 5/8
In series, which resistor has the largest voltage drop and the most power?
The largest resistor. With a common current, $V_{n} = I R_{n}$ and $P_{n} = I^{2} R_{n}$ , so both drop and power are proportional to resistance.
Rule · 6/8
What is the standard solving chain for a series circuit?
Add resistances to get $R_{T}$ , find $I = V_{S} / R_{T}$ , find each drop $V_{n} = I R_{n}$ , then check that the drops sum to the source voltage.
Common trap · 7/8
Open versus short in a series circuit: what does each do to current?
An open (broken filament, blown fuse, open switch) stops current everywhere and puts the full source voltage across the gap. A short across one resistor removes it from the total, so current rises.
Rule · 8/8
How are an ammeter and a voltmeter connected to a circuit?
Amps go in line, volts go across. An ammeter (near-zero resistance) is inserted in series in the current path; a voltmeter (very high resistance) connects in parallel across the part.

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