3 Energy and Voltage

Question 1

What is the unit for current?

Answer 1

ampere / amps or A

Question 2

Define current

Answer 2

The rate of flow of charge OR the number of coulombs passing a point in a circuit per unit time (It is not the speed of the electrons!)

Question 3

Describe what it means when 1 A is passing through a circuit

Answer 3

1 A = 1 Coulomb per second

Question 4

What is the unit for energy?

Answer 4

joules

Question 5

How is energy related to current, voltage and time?

Answer 5

E = IVt

Question 6

What is voltage measured in?

Answer 6

Volts or V

Question 7

Define voltage

Answer 7

It is the energy per unit charge either supplied by a cell, or transferred to a component.

Question 8

How does voltage related to current and resistance?

Answer 8

V=IR

Question 9

What is a volt?

Answer 9

1 V = 1 J/C 1 volt = 1 joule per coulomb

Question 10

What is resistance?

Answer 10

a measure of how much voltage is needed per amp of current. It is a measure of the is a measure of the tendency of a material to resist the flow of an electrical current.

Question 11

How is power related to current and voltage?

Answer 11

P=IV

Question 12

What is power measure in?

Answer 12

Watts (W)

Question 13

What is a watt?

Answer 13

1 W = 1 J/s I Watt = 1 joule per second

Question 14

How is voltage related to energy and charge?

Answer 14

V=E/Q

Voltage = Energy / Coulomb

Voltage lost across a component is a measure of the energy lost across the component per coulomb

Question 15

What is the voltage across a cell or power supply a measure of?

Answer 15

The energy transferred from chemical store to electrical in the wires per coulomb

Question 16

What type of circuit is this? Series or parallel?

Answer 16

Series circuit

Only one path or branch in the circuit

Question 17

What component symbols are shown below?

Answer 17

battery/two cells

&

solar cell

Question 18

What component symbol is shown below?

Answer 18

variable resistor

Question 19

What component symbol is shown below?

Answer 19

thermistor

Question 20

What component symbol is shown below?

Answer 20

ammeter

Question 21

What component symbol is shown below?

Answer 21

diode

Question 22

What component symbol is shown below?

Answer 22

buzzer

Question 23

What component symbol is shown below?

Answer 23

motor

Question 24

What component symbol is shown below?

Answer 24

voltmeter

Question 25

What component symbol is shown below?

Answer 25

bulb

Question 26

What component symbol is shown below?

Answer 26

Fuse

Question 27

What component symbol is shown below?

Answer 27

Light emitting diode

Question 28

What component symbol is shown below?

Answer 28

Light dependent resistor

Question 29

How does voltage across bulb in a series and parallel circuit differ?

Answer 29

Current is conserved in all circuits Series - current is the same everywhere in the circuit Parallel - current splits between the branches- current into a junction equals current out of a junction

Question 30

How does current differ between series and parallel circuits?

Answer 30

Current is conserved in all circuits Series - current is the same everywhere in the circuit Parallel - current splits between the branches- current into a junction equals current out of a junction

Question 31

Each bulb provides 3 V. In which circuit (series or parallel are the bulbs brighter?

Answer 31

Series- voltage is shared - V_Cell = V₁ + V₂ Parallel - each bulb gets the full voltage of the cell - V_cell = V₁ = V₂ Bulbs in parallel are brighter = both have 3V across them (brighter) Bulbs in series have 1.5 v across each (dimmer)

Question 32

Bulbs in series provide a larger resistance than bulbs in parallel With this in mind, which circuit draws a larger current from the cell?

Answer 32

V = IR I = V / R as resistance decreases, the current increases for the same voltage The second circuit draws a larger current from the cell, bulbs are in parallel and the total resistance is smaller than the first circuit (series circuit)

Question 33

Why are the bulbs dimmer in the second circuit?

Answer 33

Voltage is shared between bulbs in series Less voltage across cell therefore bulb is dimmer.

Question 34

Explain why the second circuit draws a lower current from the cell?

Answer 34

circuit with two bulbs in series - has larger resistance V=IR I = V/R as resistance increases, current decreases for same voltage

Question 35

What is true about the current in a series circuit?

Answer 35

Current is the same everywhere in a series circuit

Question 36

What happens to the total resistance and current in a circuit as more bulbs are added in **parallel**

Answer 36

Adding bulbs in parallel decreases the total resistance V=IR I = V / R as resistance decreases, current increases for the same voltage

Question 37

How does the resistance of an LDR vary with light intensity?

Answer 37

As light intensity increases, resistance decreases