07 Energy and Voltage- 4th Form Flashcards
Why would an appliance NOT need an Earth wire?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/901/q_image_thumb.png?1604838471)
It is double insulated
It has a plastic casing OR the electrical components are incased by plastic
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/901/a_image_thumb.png?1604838501)
Why are the bulbs dimmer in the second circuit?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/903/q_image_thumb.jpg?1528218808)
Voltage is shared between bulbs in series
Less voltage across each bulb therefore bulb is dimmer.
Define voltage
Energy per unit charge either supplied by a cell, or transferred to a component.
What component symbol is shown below?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/907/q_image_thumb.jpg?1527840224)
Light dependent resistor
What type of current is shown in the image?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/908/q_image_thumb.png?1604840235)
Alternating current
Current that constantly changes direction
i.e. 50 Hz or 50 times a second
What is voltage measured in?
Volts or V
What is the voltage across a cell or power supply a measure of?
The energy transferred from chemical store electrically to the wires per coulomb
What component symbol is shown below?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/911/q_image_thumb.jpg?1527840355)
bulb
What component symbol is shown below?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/912/q_image_thumb.jpg?1527840470)
ammeter
Define current
- 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!)
Which wire is circled in the image?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/914/q_image_thumb.jpg?1604830870)
Earth wire
What happens to the total resistance and current in a circuit as more bulbs are added in parallel
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/915/q_image_thumb.jpg?1528219415)
Adding bulbs in parallel decreases the total resistance
V=IR
I = V / R
as resistance decreases, current increases for the same voltage
The IV graph below shows a line for fixed resistor. How would the line change for a resistor with half the resistance?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/916/q_image_thumb.png?1604846224)
It would be steeper
It would have double the gradient
It would have double the current for the same volts
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/916/a_image_thumb.jpg?1604846234)
What is the effect of current in a resistive wire?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/917/q_image_thumb.jpg?1604838561)
Moving electrons in the wire collide with the metal ions
They transfer energy electrically to the wire
The wire heats up -gains a thermal store
When hot enough the wire may glow - radiate energy
How will the current change if the resistance of a circuit is decreased for the same voltage?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/918/q_image_thumb.jpg?1604842592)
current will increase
How does a fuse work?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/919/q_image_thumb.png?1604842681)
- If the current exceed the fuse rating (surge in current)
- the fuse wire heats up and melts
- This breaks the circuit and isolate the appliance
- protecting it from overheating/fire
To investigate how the currect varies with voltage in a filament bulb, fixed resistor and diode you should use the cirucit below.
Why does the circuit need a variable resistor?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/921/q_image_thumb.png?1604830911)
To vary the voltage across the component
Independent variable is voltage
Dependent variable is current
The plastic around wires keep us safe. Explain
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/923/q_image_thumb.jpg?1604830626)
Plastic is an insulator.
No current can flow through an insulator
no risk of electric shock
What is resistance?
- The tendency of a material to resist the flow of an electrical current.
- A measure of how much voltage is needed per amp of current.
How does the resistance vary with light intensity on a LDR?
As light intensity increases, resistance decreases
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/926/a_image_thumb.png?1604843186)
Below is an IV graph for a…..
![](https://s3.amazonaws.com/brainscape-prod/system/cm/358/976/927/q_image_thumb.png?1604840406)
diode
How is voltage related to energy and charge?
V=E/Q
Voltage = Energy / Coulomb
Voltage lost across a component is a measure of the energy lost across the component per coulomb
What is power measure in?
Watts (W)