# 3 Energy and Voltage Flashcards

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1
Q

What is the unit for current?

A

ampere / amps or A

2
Q

Define current

A

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!)

3
Q

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

A

1 A = 1 Coulomb per second

4
Q

What is the unit for energy?

A

joules

5
Q

How is energy related to current, voltage and time?

A

E = IVt

6
Q

What is voltage measured in?

A

Volts or V

7
Q

Define voltage

A

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

8
Q

How does voltage related to current and resistance?

A

V=IR

9
Q

What is a volt?

A

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

10
Q

What is resistance?

A

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.

11
Q

How is power related to current and voltage?

A

P=IV

12
Q

What is power measure in?

A

Watts (W)

13
Q

What is a watt?

A

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

14
Q

How is voltage related to energy and charge?

A

V=E/Q

Voltage = Energy / Coulomb

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

15
Q

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

A

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

16
Q

What type of circuit is this? Series or parallel?

A

Series circuit

Only one path or branch in the circuit

17
Q

What component symbols are shown below?

A

battery/two cells

&

solar cell

18
Q

What component symbol is shown below?

A

variable resistor

19
Q

What component symbol is shown below?

A

thermistor

20
Q

What component symbol is shown below?

A

ammeter

21
Q

What component symbol is shown below?

A

diode

22
Q

What component symbol is shown below?

A

buzzer

23
Q

What component symbol is shown below?

A

motor

24
Q

What component symbol is shown below?

A

voltmeter

25
Q

What component symbol is shown below?

A

bulb

26
Q

What component symbol is shown below?

A

Fuse

27
Q

What component symbol is shown below?

A

Light emitting diode

28
Q

What component symbol is shown below?

A

Light dependent resistor

29
Q

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

A

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

30
Q

How does current differ between series and parallel circuits?

A

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

31
Q

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

A

Series- voltage is shared - VCell = V1 + V2

Parallel - each bulb gets the full voltage of the cell - Vcell = V1 = V2

Bulbs in parallel are brighter = both have 3V across them (brighter)

Bulbs in series have 1.5 v across each (dimmer)

32
Q

Bulbs in series provide a larger resistance than bulbs in parallel

With this in mind, which circuit draws a larger current from the cell?

A

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)

33
Q

Why are the bulbs dimmer in the second circuit?

A

Voltage is shared between bulbs in series

Less voltage across cell therefore bulb is dimmer.

34
Q

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

A

circuit with two bulbs in series - has larger resistance

V=IR

I = V/R

as resistance increases, current decreases for same voltage

35
Q

What is true about the current in a series circuit?

A

Current is the same everywhere in a series circuit

36
Q

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

A

Adding bulbs in parallel decreases the total resistance

V=IR

I = V / R

as resistance decreases, current increases for the same voltage

37
Q

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

A

As light intensity increases, resistance decreases