Topic 03: Electric Circuits

Question 1

Conventional current flow

Answer 1

Flow from positive to negative, used to describe the direction of current in a circuit

Question 2

Current

Answer 2

The rate of flow of charge in a circuit, measured in Amperes and has symbol I

Question 3

Detecting circuit

Answer 3

A circuit with a potential divider with one of the resistors being a semiconductor, which, when an external condition changes will change its resistance change the voltage across the other resistor in the potential divider

Question 4

Diode

Answer 4

Components that allow current through in one direction. In the correct direction, diodes have a threshold voltage (typically 0.6 V) after which current flows manually

Question 5

Electromotive force (EMF)

Answer 5

The energy supplied by a source per unit charge passing through the source, measured in volts

Question 6

Electron flow

Answer 6

The flow of electrons in a circuit, from negative to positive

Question 7

Internal resistance

Answer 7

The unavoidable resistance any power source will have that makes it harder for current to flow through the source. It causes energy to be dissipated in the source

Question 8

Kirchhoff’s first law

Answer 8

The total current entering a junction is equal to the total current leaving it

Question 9

Kirchhoff’s second law

Answer 9

The sum of EMF in any loop of the circuit is equal to the sum of the potential differences of each component

Question 10

Light dependent resistors (LDRs)

Answer 10

When these components are illuminated with light, their resistance goes down. As light intensity increases, resistance decreases

Question 11

Ohmic conductor

Answer 11

A conductor following Ohm’s law where current flowing through it is directly proportional to the potential difference between each end of the conductor. This only holds if the conductor is kept at a constant temperature

Question 12

Ohm’s law

Answer 12

Electric current is proportional to potential difference and inversely proportional to resistance

Question 13

Parallel

Answer 13

When two electrical components are on separate loops to one another in a circuit. Potential difference over each loop is the same, current is split between branches

Question 14

Potential difference

Answer 14

The difference in electrical potential between two points in a circuit and the work done that is required per coulomb to move a charge from the lower potential point to the higher potential point. It is measured in volts

Question 15

Potential divider

Answer 15

A combination of two or more resistors in series. These result in the potential difference of the circuit being split into a specific ratio depending on the resistance of the resistors. They can be used to get a specific output voltage from the circuit

Question 16

Power

Answer 16

Rate of energy transfer in a circuit. It can be calculated as the product of the current and the potential difference between two points. Measured in watts

Question 17

Resistance

Answer 17

A measure of how difficult it is for current to flow in a circuit or component, measured in Ohms and has symbol R

Question 18

Resistivity

Answer 18

A measure of how difficult it is for charge to travel through a material, depending on the material’s cross-sectional area, length, and resistance. It is measured in Ohm-metres and has symbol ρ

Question 19

Semiconductors

Answer 19

Materials that change their resistance depending on external conditions

Question 20

Series connection

Answer 20

When two electrical components are on the same loop to one another in a circuit. Potential difference is split between components depending on their resistance, current is the same across all components

Question 21

Superconductor

Answer 21

A material that has zero resistivity below a critical temperature. They are used for very efficient electricity transmission or to create very strong magnetic fields, but require extreme cooling to reach their critical temperatures

Question 22

Terminal potential difference

Answer 22

The actual potential difference across the terminals of a power source. It is the source’s EMF minus the voltage drop due to the source’s internal resistance

Question 23

Thermistor

Answer 23

When these components are heated up, their resistance goes down. As temperature increases, resistance decreases

Question 24

Variable resistors

Answer 24

A resistor that can have its resistance changed. Typically, these are used with power supplies to change the voltage of a circuit without using a transformer

Question 25

Voltmeter

Answer 25

A device used to measure the potential difference between two points on a circuit, ideally it has infinite resistance so no current passes through it