This diagram represents a p-n junction diode - NSC Technical Sciences - Question 7 - 2020 - Paper 1

The symbol for a p-n junction diode consists of a triangle pointing towards a line, with the triangle representing the p-type material and the line representing the n-type material.

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In this representation, the arrow indicates the direction of conventional current flow, from p-type to n-type.

An intrinsic semiconductor, such as silicon or germanium, has four valence electrons. This allows for the formation of covalent bonds within the crystal structure.

A capacitor is an electrical component that stores electrical energy in an electric field. It consists of two conductive plates separated by an insulating material, known as a dielectric. When a voltage is applied across the plates, an electric field is created, allowing the capacitor to store charge.

The relationship between the capacitance (C) and the charge (Q) stored on the plates is given by the formula:

$Q = C imes V$

where $V$ is the voltage across the plates of the capacitor. This indicates that the charge is directly proportional to both the capacitance and the voltage.

1. Decrease the surface area of the conductive plates: Reducing the area of the plates will decrease the amount of charge that can be stored, thus decreasing the capacitance.

2. Increase the distance between the plates: By separating the plates further apart, the capacitance will decrease due to a reduction in the electric field strength between them.

First, we calculate the power consumed by the lamp using the formula:

$P = I^2 imes R$

Where:

• $I = 2 ext{ A}$
• $R = 60 ext{ Ω}$

Thus,

$P = (2 ext{ A})^2 imes 60 ext{ Ω} = 4 imes 60 = 240 ext{ W} = 0.24 ext{ kW}$

Next, we calculate the energy consumed in two hours:

$ext{Energy} = P imes t = 0.24 ext{ kW} imes 2 ext{ h} = 0.48 ext{ kW·h}$

Finally, the cost of the electricity consumed is:

$ext{Cost} = ext{Energy} imes ext{tariff} = 0.48 ext{ kW·h} imes R1.75/ ext{kW·h} = R0.84$