P5 Flashcards
What do you call a negative charge?
Electron
What do you call a neutral charge?
Neutrons
Are atoms neutral, positive or negative?
Neutral
In a helium atom where do you find neutrons electrons and protons?
Two protons in the middle
Two neutrons in the middle
= nucleus
And two electrons orbiting
What is static electricity
The build up of charge
Charge builds up and stays there “static”
When you rub a cloth against a metal rod one of the two objects end up having a negative charge (they were both neutral before)
Which one becomes negatively charged and why?
The cloth because the electrons in the rod move to the cloth so there are more electrons than protons giving the cloth a negative charge. An the rod becomes positively charged.
Can all neutrons jump from one object to the other
No. Only electrons can move
Why are metals such good conductors?
Because they have lots of free electrons.
How does lightning work?
During a thunderstorm electrons build up in clouds. Eventually they come out as lightning and all the charges go through the lightning into the ground where there are lots of protons.
What is an example or an insulator and why is it one?
Plastic - there are few free electrons so there are few charges to move.
The difference between ……… ……. Causes a flow of charge
Electrical potential
Why do you need a battery in a circuit? And how does It work?
To supply the push that makes charges flow. This push is caused by potential difference between the two terminals of the battery.
The flow of electrons is measured with…
Current (I)
How do you find resistance?
Voltage ➗ current
How do you find voltage?
Resistance ✖️ current
How do you find current?
Voltage ➗ resistance
In a series circuit resistance is calculated by…
Adding resistance together
In a series circuit the ……… Is shared between components. If the resistances are equal, the …….. Will be shared equally.
Voltage (potential difference)
In a parallel circuit is the current the same/different/stronger/weaker throughout the circuit before and after it is split?
Same
The current will be shared equally if the resistance is….
Equal
What are the differences in a parallel circuit and a series circuit?
series circuit:
-current through each of the components is the same
-the voltage across the circuit is the sum of the voltages across each component.
In a parallel circuit:
the voltage across each of the components is the same, and the total current is the sum of the currents through each component.
What do you call a positive charge?
Proton
What do you call a battery in a circuit diagram?
Cell
What are the circuit symbols for a resistor?
A rectangle
What are the circuit symbols for a variable resistor?
Rectangle with arrow going through it ↗️
What are the circuit symbols for a motor?
Circle with M inside
What are the circuit symbols for a LDR?
Rectangle with two arrows pointing down on it
What is a thermistor and an LDR?
Thermistor= heat dependent resistor LDR= light dependent resistor
What is the symbol for a thermistor?
An upside down tick over a rectangle
What are the circuit symbols for an ammeter?
Circle with A in it
What are the circuit symbols for a voltmeter?
Circle with v in it
Where does the ammeter go in a circuit?
In the loop with the component
I series
Where does a voltmeter go in a circuit?
In parallel to a component
What’s the difference between electron flow and conventional current?
Conventional = current travels from the positive to negative terminal in a circuit. Positive charge carrying electricity
Electron flow = electrons repelled from negative terminal and attracted to positive terminal.
What does current mean?
Flow of charged particles
Moving particles
What does an ammeter do?
Counts no. Or electrons passing each second
What is the difference in conductors and insulators
Condo cuties have lot of free charges that are free to move. Insulators have no free charges free to move
What is potential mean in physics?
How much energy an electron has at a given point in a circuit
What is potential difference?
The difference in how much energy and electron has between two points.
What is potential difference measured in?
Volts
How is static electricity caused?
When two insulating materials are rubbed against each other. The friction causes electrons to move from one material to the other. This results in one material being positively charged and one material being negatively charged.
What is a light dependant resistor?
A resistor who’s resistance depends on the light intensity it is exposed to. The greater the light intensity the smaller the resistance.
Therefore current increases
What is a thermistor?
A resistor whose resistance depends upon heat intensity. The greater the heat intensity the smaller the resistance.
Therefore the current increases
How do you double the current in a series circuit?
Add an extra cell. This will double the current due to the voltage doubling.
How would you make the circuit last longer without doubling the voltage?
Add an extra cell parallel to the circuit
Do series or parallel circuits have the same potential difference when adding an additional cell?
Parallel circuit.
What happens when you move a wire into a magnetic field?
A voltage is induced when there is relative movement between the two. If the wires direction of movement is reversed the direction of current also reverses.
How can you increase a current in a magnetic and electric current?
Using a stronger magnet. Moving the wire faster.
How is a voltage induced between a magnet and coil of wire?
The coil of wire continuously ‘cut’ the magnetic field with the current travelling through it. So a voltage is induced.
This is called electromagnetic induction.
A larger voltage is induced between a coil and wire if:
- The strength of the magnet is increased.
- The number of turns on the coil is increased.
- An iron core is inside the wire.
- the rate at which the coil is turned increases.
As a coil rotates it cuts the magnetic fiend at different rates. If the wire Is at right angle to the field lined, does it cut any field lines?
No.
Therefore there is no voltage induced.
As a coil rotates it cuts the magnetic fiend at different rates. If the wire Is parallel to the field lines what is the rate of cutting?
It’s at its maximum.
The voltage induced is at its peak.
Why does the voltage induced from a coil and wire alternate?
The coil rotates and therefore cuts the angle at different directions.
What does d.c stand for?
Direct current = current flows in the same direction.
What does a.c stand for?
An alternating current.
The current changes direction at regular intervals.
At what voltage is mains electricity put it to household appliances?
230V
Is the UKs power supply a.c or d.c? And why?
a.c.
Because it’s easier to generate in large Amounts
What are motors used in?
Hair dryers. DVD players.
