Parallel Circuits

In a parallel circuit, there is more than one way for charge to flow. The components are in different loops, which we call branches.

Below is an example of a parallel circuit:

In this parallel circuit, there’s a lamp that isn’t in the same loop as the others We add a second loop of wire, so the second lamp is in its own loop of wire. The circuit has lines and components parallel to each other, hence the name ‘parallel circuit’.

Circuit Rules

In a parallel circuit, electrons don’t pass through every component. This means that if a component in one branch breaks, components in other branches continue to work.

Current in a parallel circuit

In a parallel circuit, the current is shared between the different branches. We measure the current using an ammeter, which is placed in series with the components.

  • Current is measured in amperes (A)

We can express this as:

Itotal = I1 + I2 +I3

In other words, the total current in a parallel circuit equals the sum of the currents of each separate branch.

The current in each branch sums up to the total current since it’s shared among the branches. For example, if the total current is 6 amperes, all the branches must add up to 6 amperes. Each branch is 2 amperes and there are three branches, which adds up to 6 amperes (2 + 2 + 2 = 6).

Keep in mind that the ammeter should be placed next to the component you are measuring.

Since we’re using identical components (the lamps), the same current is expected to flow through each branch. In this case, we have 2 amps for all three branches.

Potential difference in a parallel circuit

In a parallel circuit, the potential difference across each branch is the same as the potential difference across the cell or the battery.

  • Potential difference (V) is measured in volts (V).

We can express this as:

Vtotal = V1 = V2 = V3

In other words, the potential difference across each branch is equal.

Example:

If the potential difference going across the cell is 4 volts, then the potential difference going across each lamp will also be 4 volts. This applies to any other components in a circuit, not just lamps.

Resistance in a parallel circuit

When resistors are connected in parallel, their combined resistance is lower. This is because the current can take multiple paths.

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