Series and parallel circuits
Wire two or three bulbs in series and in parallel, compare their brightness and the current, take one bulb out, and calculate the total resistance.
Core concept
In series one current flows through everything and resistances add; in parallel each branch gets the full voltage and the total resistance falls
Topic: Electricity
In a series circuit: A complete loop that electricity flows around, from the cell through the bulb and back. All key words the components are joined one after another, so there is only one path: the same current: The flow of electricity through a wire, measured in amperes (A). All key words flows through each, and the battery's voltage: The push that makes electricity flow, measured in volts (V). All key words is shared between them. Resistances in series add: R = R₁ + R₂ + …. In a parallel circuit each component is on its own branch, so each gets the full battery voltage and the currents in the branches add up. For resistances in parallel, 1/R = 1/R₁ + 1/R₂ + …, so the total resistance: How much something slows down the flow of electricity, measured in ohms (Ω). All key words is less than any one branch. House wiring is in parallel so each light can be switched on and off by itself.
What you will learn
- Compare the brightness of bulbs in series and in parallel.
- Explain what happens when one bulb is removed from each kind of circuit.
- Calculate equivalent resistance for series and parallel combinations.
Before you start
- Know that current is measured in amperes and resistance in ohms.
Materials
- 6 V battery pack
- Three bulbs in holders (6 Ω each) and a 12 Ω bulb
Equipment
- Ammeter and connecting wires
Procedure
- Join two bulbs in series to the 6 V battery and record the current and brightness.
- Join the same two bulbs in parallel and compare.
- Take bulb A out of each circuit and record what happens to the others.
- Use three bulbs, and change bulb B to 12 Ω, and calculate the total resistance each time.
How this simulation is simplified
- The battery gives a steady 6 V; the bulbs keep a fixed resistance and the wires have none.
- Brightness is shown relative to one 6 Ω bulb across the full 6 V (6 W).