Series and Parallel Connections; the Rheostat
Two ways to wire components together — and one clever device that lets you turn the current up or down.
Big idea: There are two basic ways to connect resistors (lamps, heaters, motors) in a circuit. In a series connection they sit on one single path, so the same current passes through all of them. In a parallel connection they sit on separate branches, so they all feel the same voltage. Knowing which is which lets you predict the current, and a rheostat lets you change it on purpose.
By the end you will be able to:
- state the three rules for a series connection (current, voltage, resistance),
- state the three rules for a parallel connection,
- find the total resistance of a simple mixed circuit,
- explain how a rheostat controls the current in a circuit.
1. Quick recap: current, voltage, resistance
You already met these in the last two topics. Let us line them up:
- Current I (in amperes, A) is how much charge flows per second past a point.
- Voltage U (in volts, V) is the electrical "push" that drives the current across a part of the circuit.
- Resistance R (in ohms, Ω) is how strongly a component opposes the current.
Ohm's law for a section of a circuit ties them together: I = U / R, which we can also write as U = I · R. Every rule in this lesson is really just Ohm's law applied carefully to each part of the circuit.