P3.2

Question 1

what is a fuse

Answer 1

a safety device which breaks the circuit if the current is too high

Question 2

what does a fuse contain and how does it work?

Answer 2

a fuse contains a thin wire which melts if the current is too high

Question 3

what is the rule of fuses?

Answer 3

work out the current and choose the next fuse up

Question 4

what is the total potential difference when two or more cells are connected in series?

Answer 4

the sum of the potential differences

Question 5

what is the total voltage when an identical cells is placed in parallel with the original cell?

Answer 5

the voltage stays the same

Question 6

what is the equation for energy?

Answer 6

energy = charge x voltage

Question 7

series circuit

Answer 7

when all components in a circuit are connected to each other in one loop

Question 8

how is an ammeter connected in a circuit?

Answer 8

in series

Question 9

what is the current in a series circuit?

Answer 9

the same everywhere

Question 10

how is a voltmeter connected in a circuit?

Answer 10

in parallel

Question 11

what is potential difference in a series circuit?

Answer 11

shared equally between components

Question 12

parallel circuit

Answer 12

has components connected in more than one loop

Question 13

what is current in a parallel circuit?

Answer 13

it’s shared between loops

Question 14

what is potential difference in a parallel circuit?

Answer 14

the same everywhere

Question 15

what is the equation for voltage?

Answer 15

voltage = current x resistance

Question 16

what is resistance measured in?

Answer 16

Ohms Ω

Question 17

what is the total resistance in a parallel circuit?

Answer 17

always smaller than the smallest resistance in the circuit

Question 18

How does resistance change?

Answer 18

-sometimes you can vary the resistance of an object, like a variable resistor
-the resistance of other objects can vary as current passing through it increases
-the resistance of other objects like fixed resistors never changes

Question 19

what are the expected results for a voltage - current graph for a filament bulb?

Answer 19

The filament wire is heated up by the current. As the wire heats up the positive ions in the wire vibrate more, making it harder for electrons to get through and therefore increasing the resistance

Question 20

what are the expected results for a voltage - current graph for a diode?

Answer 20

Where the current is zero the resistance is very high. When the p.d. reaches a certain level in the forward direction the resistance reduces.

Question 21

what are the three equations for power?

Answer 21

1. power = energy / time
2. power = voltage x current
3. power = resistance x current ^2

Question 22

describe the current - voltage graph for LDR

Answer 22

As light intensity increase more electrons are released from the semi conductor and the resistance decreases.

Question 23

describe the current - voltage graph for thermistor

Answer 23

As the temperature increases, more electrons have enough energy to escape from the semi conductor atoms and a resistance decreases

Question 24

how can the total resistance of resistors in series be found?

Answer 24

adding the values of the individual resistors together