A parallel circuit is an electric circuit in which the electric current has more than one path to follow. The advantage is that, like adding another lane on a busy freeway, more traffic can flow. With a parallel circuit, more electric current can flow.
In this project, you will determine the path that electrons follow in a parallel circuit. You will measure the total current and voltage of each circuit as well as the connected branches, and you will use these measurements to confirm Ohm's law. You will also investigate how battery cells are connected in parallel and the effect of parallel cells on the current and voltage of a circuit.
Purpose: To determine the path of the electric current in a parallel circuit.
- 1.5-volt battery
- battery holder with insulated wires (red and black)
- 2 identical flashlight lamps (for E-10 screw-base holder)
- 2 lamp holders with E-10 screw-base
- wire cutter
- 12-inch (30-cm) piece of 22-gauge insulated wire
- screwdriver with head type for lamp holder screws
- Place the battery in the battery holder.
- Screw the lamps into the lamp holders.
- Use the wire cutter to cut the wire into two 6-inch (15-cm) parts. Then strip about 1⁄2 inch (1.25 cm) of insulation from each end of the wires.
- Attach the wires to connect the lamp holders, as shown in Figure 49.1.
- Holding the insulated part of the wires attached to the battery holder, touch the bare ends of the wires to the screws on either side of one of the lamp holders, as shown in Figure 49.1. Compare the brightness of the lamps. CAUTION: Do not leave the wires on the screws for more than 5 to 6 seconds. The bare wire and lamp can get hot enough to burn you. Allow them to cool before touching them.
The lamps glow with equal brightness.
The electric current has more than one path to follow through the connected lamps in this experiment, so the circuit formed what is called a parallel circuit. The arrows in the electrical schematic in Figure 49.2 indicate the movement of the current (e´) away from the negative terminal of the battery through the bulbs, then back to the positive terminal of the battery. At junction A (one of the screws on the side of lamp base 1), the current divides before moving through the lamps. Then the current recombines at junction B (one of the screws on the opposite side of lamp base 1) and returns to the positive terminal of the battery. The facts that the lamps are identical and glow with equal brightness show that the same amount of current reaches both lamps.
Try New Approaches
- Would it affect the brightness of the lamps if more lamps were connected in parallel? Repeat the experiment, adding more lamps.
- Would it affect the brightness of the lamps connected in parallel if a lamp is placed in series with them? Repeat the original experiment, connecting two lamps as in the original investigation and adding a third lamp in series, as shown in the schematic in Figure 49.3.