P3.2 -

Question 1

what is the role of an ammeter?

and where is it positioned in a circuit?

Answer 1

measures current in a circuit

in line with the component - as the current needs to flow THROUGH them

Question 2

what is the role of a voltmeter?

and where is it positioned in a circuit?

Answer 2

measures the difference in voltage between two points

is positioned on both sides of a component - or on another ‘branch’

Question 3

in a series circuit, describe the features of:

a) current
b) potential difference
c) resistance

Answer 3

a) current - is equal across all components
b) total pd is equal to addition of all pds
c) res - of all components is different

Question 4

in a parallel circuit, describe the features of:

a) current
b) potential difference
c) resistance

Answer 4

a) current - split between different branches NOT EQUAL
b) pd across all components are equal
c) res - of all components are different
also: the greater the resistance, the smaller the current going through it. (most electrons want to do easiest things in life, so most electrons go through least resistance)

Question 5

in a symbol of a cell, which one is positive and which is negative?

Answer 5

long one = positive

short one = negative

Question 6

what two factors does current depend on?

Answer 6

• resistance
• potential difference

Question 7

what is the equation to calculate potential difference?(give units and full words)

Answer 7

V = IR

potential difference (V) = current (A) x resistance (Ω)

Question 8

define potential difference

Answer 8

the difference in voltage between two points

Question 9

what is the difference between a variable resistor and a normal resistor?

Answer 9

a variable resistor’s resistance can change, a normal resistor’s resistance cannot

Question 10

how does a battery cause a current to flow in a circuit?

Answer 10

in a cell, the positive terminal is at a higher electric potential than the negative terminal.

and so there is a POTENTIAL DIFFERENCE in which the electrons move from the higher energy terminal to the other (to balance out)

Question 11

what is the equation to calculate the energy transferred in a circuit?

Answer 11

E = V x Q

energy transferred (J) = potential difference (V) x charge (C)

Question 12

state the factor which allows the transfer energy in a circuit

Answer 12

resistance

Question 13

explain how a hotter wire affects the resistance

Answer 13

• in wire/component, ions usually vibrate up and down
• vibrating ions get more energy so they vibrate faster
• so more electrons collide with the ions

SO MORE RESISTANCE AS MORE ENERGY IS TRANSFERRED BY CURRENT

Question 14

describe current (2)

Answer 14

Current is the rate (1) of flow of charge (1)

Question 15

describe voltage (1)

Answer 15

Voltage is a measure of the energy carried (1) by the current per coulomb of charge (1)

Question 16

describe potential difference (2)

Answer 16

Potential difference is a measure of the work done (1) per coulomb of charge (1)

(diff in voltage between two points)

Question 17

role of variable resistor?

Answer 17

to alter the current

Question 18

the higher the resistance, the less energy transferred by current as it passes through resistance.

true or false?

Answer 18

false.

The higher the resistance, the more energy transferred by the current as it passes through the resistance.

Question 19

what is a sensor circuit?

Answer 19

A sensor circuit is a circuit which turns a component on/off automatically, in response to external stimuli.

Question 20

if confused abt LDR, watch this video:

Answer 20

https://youtu.be/GU1F-EgXFAQ?feature=shared

Question 21

a) Draw the circuit of a LDR-based street lamp (2)
b) Explain how street lamps work (6).

Answer 21

a)

|———– il————|
| |
| fixed resistor
| |
| |————
| LDR |
| | indicator (lamp)
| | |
|—————————————. (2)

b)

Any 3 from:
- at low light levels, resistance in LDR is higher than at high light levels
- thus a greater proportion of current goes through the lamp than at high light levels
=> since the Lamp resistance: LDR resistance is lower
- this amount of current flowing through the lamp is high enough to switch it on

Any 3 from:
- at high light levels, resistance in LDR is low
- thus a smaller proportion of current goes through the lamp than at low light levels
=> since the Lamp resistance: LDR resistance is higher
- this amount of current flowing through the lamp is not high enough to switch it on

Question 22

Draw symbol for:

• fixed resistor
• variable resistor
• diode
• LED
• LDR
• thermistor
• indicator
• motor
• ammeter
• open switch
• closed switch
• cell
• battery
• fuse
• heater
• voltmeter

Answer 22

all on 10A physics onenote

Question 23

what is a battery

Answer 23

two or more cells joined together

Question 24

what is an indicator

Answer 24

something that indicates that a current works

Question 25

what is a diode

Answer 25

something that allows a current to only flow in one direction

Question 26

what is the purpose of a fuse

Answer 26

to stop the current from getting too high (by exploding before that point)

Question 27

purpose of voltmeter

Answer 27

measure p.d

Question 28

purpose of ammeter

Answer 28

measures current

Question 29

as light levels increase, what happens to the resistance of LDR?

Answer 29

resistance decreases

Question 30

at temp increases, what happens to resistance of thermistor?

Answer 30

resistance decreases