Physics - Electric Circuits

Question 1

Circuit symbols: ammeter, voltmeter, cell, battery, switch, diode, variable resistor, resistor, light source

Answer 1

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Question 2

What is direct current?

Answer 2

Direct current is when the flow of charge is always uni-directional. It can be defined as a constant flow of electrons from a high electron density to a low electron density. It is used in common batteries

Question 3

What is alternating current?

Answer 3

Alternating current is when the flow of charge periodically changes its magnitude from positive to negative. The current and voltage looking similar to a sine wave. The frequency is: amount of cycles / time periods
This is commonly used in household sockets

Question 4

How can you convert AC to DC?

Answer 4

Diodes.

A diode is a semiconductor, this means it only permits the flow of current in one direction, so converts AC to DC

Question 5

What is a conductor?

Answer 5

A conductor is a material that allows the flow of electrons or thermal energy through it

Question 6

What is an insulator?

Answer 6

An insulator doesn’t allow the flow of electrons

Question 7

What is the equation for current?

Answer 7

Current = charge/time

Question 8

What is current and how is it measured?

Answer 8

An electrical current is a transfer of charge. The charge is the total movement of electrons measured in coulombs.
It is measured in amps (A) by an ammeter

Question 9

What is voltage and how is it measured?

Answer 9

Voltage is an electrical force that drives a current around a circuit, similar to a pushing force.
It is a difference in electrical potential

Question 10

Equation for resistance

Answer 10

Resistance = volatage/current

Question 11

Volateg - current graphs for a fixed resistor

Answer 11

As the voltage increases the current also increases by the same ratio, they are directly proportional so the graph forms a straight line through the origin

Question 12

Voltage - current graphs filament lamp

Answer 12

As the lamp heats up the resistance within it increases, this causes an S shaped graph

Question 13

What is an NTC thermistor?

Answer 13

Negative temperature coefficient thermistor.

When the temperature within an NCT increases the resistance decreases

Question 14

What is an LDR?

Answer 14

Light dependent resistor.

As the light intake increases the resistance of the LDR increases, this means it can be used in light sensitive lighting

Question 15

Current, volate and resistance in a series circuit

Answer 15

In a series circuit all the components are in a loop, this means that the current throughout the circuit is constant, the voltage of the power supply is equal to the voltage of all other components.
The total resistance is that of all components added

Question 16

Current, volate and resistance in a parallel circuit

Answer 16

In a parallel circuit components are in different, conjoined loops. The current is shared between these loops, this means that’s the total current throughout the circuit is that of all of the loops combined. The voltage of the power supply is equal to that of each loop.
As there is multiple paths for the current to take, the resistance is less than that of the most resistive strand

Question 17

Volatage equation

Answer 17

Voltage = potential energy / charge

Change in volatage = change in potential energy / charge

Question 18

Power equations

Answer 18

Power = current x voltage 
Power = (voltage/current) x current² = resistance x current²

Power = energy transferred / time
Power = work done / time