P2.3 Currents in electrical circuits

Question 1

What does the current in an ELECTRIC CIRCUIT depend on?

Answer 1

• The resistance of the components

- and the supply

Question 2

What happens when certain insulating materials are rubbed against each other?

Answer 2

They become electrically charged

Question 3

Describe, in terms of sub-atomic particles, static electricity

Answer 3

Negatively charged electrons are rubbed off one material and onto the other

Question 4

What happens when two electrically charged objects are brought together?

Answer 4

They exert a force on each other

Question 5

Opposites…

Answer 5

…attract

Question 6

What is electric current?

Answer 6

A flow of electric charge

Question 7

What is the size of the electric current equal to?

Answer 7

The rate of flow of electric charge

Question 8

What is charge measured in?

Answer 8

Coulombs, C

Question 9

What does the p.d. between two objects in an electric circuit equal?

Answer 9

• The work done
• per coulomb of charge
• that passes between the two points

Question 10

What are current–potential difference graphs used to show?

Answer 10

How the CURRENT through a component VARIES with the P.D. across it.

Question 11

Describe what you would see on a current-p.d. graph for a resistor at a constant temperature.

Answer 11

Positive line /

Question 12

What is resistance measured in?

Answer 12

Ω Ohms

Question 13

The current through a resistor (at a constant temp) is directly proportional to what?

Answer 13

P.d. across the resistor

Question 14

The current through a COMPONENT depends on what?

Answer 14

Its resistance.

Question 15

The greater the resistance…

Answer 15

…the smaller the current for a given p.d. across the component

Question 16

How do you find the p.d. provided by cells connected in series?

Answer 16

Sum of the p.d. of each cell

Question 17

In a SERIES circuit, describe: (a) How to find the total resistance (b) How the current is shared (c) How the p.d. is shared

Answer 17

(a) SUM of resistance of each component
(b) SAME current
(c) Total p.d. of the supply is SHARED between the components

Question 18

In a PARALLEL circuit, describe: (a) How to find the total current (b) How the p.d. is shared

Answer 18

(a) Sum of currents through the separate components BECAUSE CURRENT IS SHARED
(b) P.d. is same

Question 19

As the temperature of the filament increases, what happens to the resistance?

Answer 19

Resistance increases

Question 20

Is the current through a diode a.c. or d.c.? Why?

Answer 20

DIRECT

The diode has a very high resistance in the reverse direction

Question 21

When does an LED emit light?

Answer 21

When a current flows through it in a forward direction

Question 22

As temperature increases, what happens to the resistance of a thermistor?
As light increases, what happens to the resistance of an LDR?

Answer 22

They both decrease