Electricity and Magnetism - SS1 Physics Past Questions and Answers - page 2

Capacitance is a measure of a capacitor's ability to store electric charge. It is defined as the ratio of the magnitude of the charge stored on one of the capacitor's plates to the potential difference (voltage) across the plates. Capacitance depends on factors such as the size and shape of the capacitor, the distance between the plates, and the dielectric material used. A higher capacitance value indicates a greater ability to store charge and energy. When a capacitor is connected to a voltage source, it charges up by accumulating charge on its plates. The stored charge represents stored electrical energy that can be released when needed.

The capacitance of a capacitor is affected by several factors. Firstly, the surface area of the plates plays a role. A larger plate area increases capacitance because there is more space for the charge to accumulate. Secondly, the distance between the plates affects capacitance. A smaller distance results in a higher capacitance as the electric field between the plates is stronger.

Thirdly, the dielectric material placed between the plates influences capacitance. Different dielectric materials have different dielectric constants, which affect the capacitance value. Finally, the number of plates in a capacitor also affects capacitance. Adding more plates in parallel increases the effective plate area and thus increases capacitance.

The magnitude and direction of the magnetic force on a charged particle depend on three factors: the magnitude of the charge (q) of the particle, the velocity (v) of the particle, and the strength and direction of the magnetic field (B). The magnitude of the magnetic force is given by the equation F = qvBsinθ, where θ is the angle between the velocity vector and the magnetic field vector. The direction of the magnetic force is perpendicular to both the velocity vector and the magnetic field vector, following the right-hand rule.

When a charged particle moves parallel to the magnetic field lines, the magnetic force acting on it is zero since the angle between the velocity vector and the magnetic field vector is 0°, resulting in no deflection. When the particle moves perpendicular to the magnetic field lines, the magnetic force acts as a centripetal force, causing the particle to move in a circular path.

The radius of the circular path can be determined using the equation r = mv / (qB), where r is the radius, m is the mass of the particle, and q is its charge. When the particle moves at an angle to the magnetic field lines, the magnetic force acts as a combination of a centripetal force and a deflecting force, causing the particle to move in a curved path.