Benjamin Franklin began experimenting with electricity during the 18th century - Leaving Cert Physics - Question 11 - 2022

An ammeter (or galvanometer or multimeter) is used to measure electric current.

To draw the circuit diagram, you need to represent the battery as a pair of parallel lines (long line for positive, short for negative), the light bulb as a circle with a cross inside, and the switch as a break in the line connecting the battery to the bulb. Connect the components in a series circuit.

Wires in a circuit are made of metal because metals are good conductors of electricity. They have free electrons that can move easily through the metal structure, allowing electric current to flow with minimal resistance.

The subatomic particle that acts as the charge carrier in a metal is the electron.

The current (I) can be calculated using the formula:

$I = \frac{Q}{t}$

where $Q$ is the charge and $t$ is the time. Substituting the values:

$I = \frac{30 C}{6 s} = 5 A$

The potential difference (V) can be calculated using Ohm's law, which states:

$V = I \times R$

where $I$ is the current and $R$ is the resistance. Substituting in the known values:

$V = 5 A \times 3 Ω = 15 V$

The total resistance ($R_t$) of two resistors in parallel can be calculated using:

$\frac{1}{R_t} = \frac{1}{R_1} + \frac{1}{R_2}$

Substituting in the values:

$\frac{1}{R_t} = \frac{1}{3 Ω} + \frac{1}{2 Ω}$

This gives:

$\frac{1}{R_t} = \frac{2}{6} + \frac{3}{6} = \frac{5}{6}$

Thus, $R_t = \frac{6}{5} = 1.2 Ω$

To find the resistance of a 3 m piece of wire, we use the formula for resistance, which states that resistance is directly proportional to length:

$R = \rho \frac{L}{A}$

Given that the resistance of the 1.5 m piece is 12 Ω, the resistance of a 3 m piece (which is double the length) will be:

$R = 2 \times 12 Ω = 24 Ω$

The resistance of a wire is inversely proportional to its cross-sectional area. This means that as the cross-sectional area increases, the resistance decreases, and vice versa. This relationship can be expressed mathematically as:

$R \propto \frac{1}{A}$