P2.3 Currents in electrical circuits

Question 1

What is the electric current?

Answer 1

The flow of electric charge

Question 2

The size of the electric current is the…

Answer 2

Rate of flow of electric charge

Question 3

What is the equation for the size of a current?

Answer 3

Q
I = —–
t

Question 4

What is the current measured in?

Answer 4

Amps, A

Question 5

What is the charge measured in?

Answer 5

Coulombs, C

Question 6

What does the I stand for?

Answer 6

Current

Question 7

What does the Q stand for?

Answer 7

Charge

Question 8

The voltage is also known as the…

Answer 8

Potential difference

Question 9

What is the potential difference between two points in an electric circuit?

Answer 9

The work done (energy transferred) per coulomb of charge that passes between the points

Question 10

What is the equation for potential difference?

Answer 10

W
V = ——
Q

Question 11

What is potential difference measured in?

Answer 11

Volts

Question 12

What is the work done measured in?

Answer 12

Joules

Question 13

What does the W stand for?

Answer 13

Work done

Question 14

What does the V stand for?

Answer 14

Potential difference / voltage

Question 15

What are thermistors used for in circuits?

Answer 15

Temperature sensors in fire alarms for example

Question 16

What are LDRs used for in circuits?

Answer 16

To detect light levels, e.g. automatic security lights

Question 17

What are current-potential graphs used to show?

Answer 17

How the current through a component varies with the potential difference across it

Question 18

How can the resistance of a component be found?

Answer 18

By measuring the current through, and potential difference across, the component

Question 19

The current through a resistor (at a constant temperature) is directly proportional to…

Answer 19

The potential difference across the resistor

Question 20

What is the equation for calculating the current, potential difference or resistance?

Answer 20

V = I x R

Question 21

What is resistance measured in?

Answer 21

Ohms

Question 22

What does the R stand for?

Answer 22

Resistance

Question 23

What does the current through a component depend on?

Answer 23

Its resistance

Question 24

The greater the resistance…

Answer 24

The smaller the current for a given potential difference across the component

Question 25

What is the potential difference provide by cells connected in a series the sum of?

Answer 25

The potential difference of each cell (depending on the direction in which they are connected

Question 26

For components in a connected series, the total resistance is the...

Answer 26

Sum of the resistance of each component

Question 27

For components in a connected series, there is the same...

Answer 27

Current through each component

Question 28

For components in a connected series, the total potential difference of the supply is...

Answer 28

Shared between the components

Question 29

For components connected in parallel, the potential difference...

Answer 29

Across each component is the same

Question 30

For components connected in parallel, the total current through the whole circuit is the...

Answer 30

Sum of the currents through the separate components

Question 31

The resistance of a filament bulb increases as the...

Answer 31

Temperature of the filament increases

Question 32

When does an electron current flow?

Answer 32

When electrons move through the conductor

Question 33

What can happen to electrons when traveling through the conductor?

Answer 33

They can collide into the ions from the metal

Question 34

What does the collision of electrons and ions cause?

Answer 34

Resistance as it makes it much more difficult for the current to flow

Question 35

Why is the resistance of a long wire greater than the resistance of a shorter wire?

Answer 35

Because the electrons collide with the ions more often

Question 36

Why is the resistance of a thin wire greater than the resistance of a thicker wire

Answer 36

A thin wire has fewer electrons to carry the current

Question 37

The current of a diode flows in...

Answer 37

One direction only

Question 38

The diode has a very high resistance in...

Answer 38

The reverse direction of that which they travel

Question 39

An LED emits light when the current flows through it in...

Answer 39

The forward direction

Question 40

Why is there an increasing use of LEDs for lighting?

Answer 40

It requires a much smaller current and is therefore much cheaper

Question 41

The resistance of a light-dependant resistor (LDR) decreases as...

Answer 41

The light intensity increases

Question 42

The resistance of a thermistor decreases as...

Answer 42

The temperature increases