James Clerk Maxwell, a Scottish physicist, is considered the greatest theoretical physicist of the nineteenth century - Leaving Cert Physics - Question 9 - 2018

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A magnetic field is a region where magnetic forces are felt. It is produced by moving electric charges, such as electric currents, and can be visualized through magnetic field lines that indicate the direction and strength of the field.

The magnetic field around a long straight current-carrying wire can be represented by concentric circles centered on the wire. The direction of the field lines is indicated by arrows pointing in a circular direction according to the right-hand rule.

The magnetic field inside a current-carrying solenoid is uniform and parallel to the axis of the solenoid. Outside, the field lines spread out and are weaker. The field lines can be labelled as arrows indicating the direction of the magnetic field.

Faraday's law states that the electromotive force (emf) induced in a circuit is proportional to the rate of change of magnetic flux through the circuit.

An experiment could involve a coil connected to a galvanometer. By moving a magnet relative to the coil, or by moving the coil relative to a stationary magnet, the galvanometer will show a deflection indicating an induced current.

The average emf can be calculated using the formula:

$E = - \frac{\Delta \Phi}{\Delta t}$

where:

• $\Delta \Phi = B \cdot A = (50 \text{ mT}) \times (0.2 \, \text{m})^2 = 2\times 10^{-3} \, \text{Wb}$
• $\Delta t = 1 \, \text{s}$

Thus, the average emf is: $E = \frac{2\times 10^{-3} \text{Wb}}{1 \, \text{s}} = 0.32 \, ext{V}$

Light is detected in the retina, which contains photoreceptor cells (rods and cones) that convert light into electrical signals.

• Ultraviolet (UV) rays
• X-rays