Chapter 7: (Applications of electric circuits)

Question 1

7A:
Define a “Voltage divider.”

Answer 1

A voltage divider is an electrical circuit that comprises of two resistors connected in series, achieving an output voltage that is less than the input voltage.
Here, the output voltage is defined as the voltage drops across one of the resistors, with the other resistor having a higher resistance, meaning it’ll consume most of the Voltage.

Question 2

7A:
Describe the resistance of light bulbs.

Answer 2

As current flows through a light bulb, electrical potential energy is transferred into light energy, producing light and also causing the component to heat up and have resistance.
If the current across the light bulb is greater, due to a higher applied voltage, the resistance of the component will be higher as well, meaning light bulbs are not ohmic devices.

Question 3

7A:
Define “Internal resistance.”

Answer 3

Any resistance that is associated with a source of potential difference in a circuit is known as “Internal resistance.” This increases the total resistance of the circuit as a whole, being modeled as Resistor “i,” which is in series with the voltage source.

Question 4

7A:
Define a “Diode.”
Define a “Light emitting Diode.”

Answer 4

A Diode is a semiconductor that only allows current to flow in one direction.
A light-emitting diode (LED) is a particular type of Diode that emits light when a current passes through it, given electrical potential energy is transferred into light energy.

Question 5

7A:
Define an “Anode.”
Define a “Cathode.”

Answer 5

An Anode is an electrode of a device for which current flows into a Diode.
A Cathode is an electrode of a device for which current flows out of a Diode.

Question 6

7A:
Define the term “Threshold voltage.”

Answer 6

The minimum voltage drop across a diode which is required for an electric current to flow.

Question 7

7A:
Define a “Potentiometer.”

Answer 7

A kind of resistor that has a fixed length of resistive material, and the control of the sliding contact of the resistor will dictate its value of resistance.

Question 8

7A:
Define a “Transducer.”

Answer 8

Any device which transforms energy between different forms is known as a transducer.
An input transducer transforms differing forms of energy (such as light) into electrical potential energy.
An output transducer transforms electrical potential energy into other forms of energy.

Question 9

7A:
Define a “Thermistor.”

Answer 9

This is a kind of resistor which has a variable resistance that changes with temperature.

Question 10

7A: Define a “Light dependent Resistor.”

Answer 10

This is a kind of resistor where the resistance decreases as the intensity of light hitting the component increases. These are commonly referred to as “LDRs.”

Question 11

7B:
Define “Direct current.”

Answer 11

This refers to a current where electrons flow in a constant direction, being achieved when there is a constant potential difference between the positive and negative terminal.

Question 12

7B:
Define “Alternating current.”

Answer 12

An AC circuit can have varying directions of current (electron flow) in the circuit. To produce AC, the potential difference between the positive and negative terminals is not fixed.

Question 13

7B:
Define the “Active wire.”

Answer 13

The Active wire is connected to the voltage source in a circuit and can apply both a positive maximum voltage and a negative maximum voltage, which then influences the direction of the current in the circuit.

Question 14

7B: Define the “Neutral wire.”

Answer 14

The neutral wire is connected to the opposite end of the Voltage source, being connected to the ground and having a fixed voltage of zero Volts.

Question 15

7B:
Explain the meaning of “RMS voltage/current.”

Answer 15

The RMS voltage/current is a constant level of Voltage (in this instance) under a DC circuit that would have an equivalent power loss to a varying voltage under an AC electrical system, depending on the peak voltage of that circuit.

Question 16

7B:
Describe the purpose of a “distribution board,” in household circuits.

Answer 16

The distribution board is located within household circuits and connects the active wire to the neutral wire, comprising of many features.

Question 17

7B:
Define a “circuit ring.”

Answer 17

An individual parallel circuit which forms part of a larger household circuit and services a particular appliance. All circuit rings in a household circuit are connected in parallel to ensure that current flows independently, and that any damage done to one circuit ring won’t affect the entirety of the household circuit.

Question 18

7C:
Describe the function of a “Fuse,” and outline its purpose.

Answer 18

A fuse is a safety device located in a circuit that melts when the current passing through the device is excessive, breaking the circuit connection and preventing current from flowing.
The purpose of this device is to prevent a circuit from overheating or catching fire.

Question 19

7C:
Describe the function of a “Circuit breaker,” and outline its purpose.

Answer 19

A circuit breaker is a safety device that will automatically (through the power of magnetic fields) open a switch in a circuit when the current is too high, breaking the circuit connection and preventing the flow of current. This switch is reset-able though, being preferred over fuses.
The purpose of this device is to prevent a circuit from overheating or catching fire.

Question 20

7C:
Describe the function of an “Earth Wire,” and outline its purpose.

Answer 20

An Earth wire is an alternative pathway for current to travel at the exterior of an electrical appliance to the ground as it has a low value of resistance.
The purpose of an Earth Wire is to prevent people from an electric shock if they come into contact with the exterior of an electrical appliance.

Question 21

7C:
Describe the function of a “Residual current Device,” and explain its purpose.

Answer 21

A Residual current device (RCD) will detect if there is a difference in current between the active wire and the neutral wire, shutting off the circuit imminently in this occurrence. As this would indicate that the current is traveling in the wrong direction, which can lead it to reach the exterior of an appliance and cause an electric shock.
Thus, the purpose of an RCD is to prevent an electric shock.

Question 22

7C:
List some effects of an electric shock.

Answer 22

: Irregular heart beating
: Prevention of blood circulation
: Severe burns

Question 23

7C:
Identify some treatments to an electric shock.

Answer 23

: A defibrillator can be used to restore the beating of the heart after a shock.
: An artificial respirator can be used to restore breathing patterns after the occurrence of a shock.

Question 24

7C:
Define a “short circuit.”

Answer 24

This describes the occurrence of a circuit’s current flowing through an unintended seciton due to a really low