Topic 10 - Electricity and Circuits Flashcards
What are most electrical appliances connected to?
+The mains supply by three core cables
+This means that they have three wires inside them, each with a core of copper and a coloured plastic coating
+The colour of the insulation on each cable shows its purpose
What are parallel circuits?
+Circuits where electrical components are connected alongside one another forming extra loops
+If a bulb is broken, the current can still flow through other components in the circuit through the other loop.
+When a bulb goes out, other components can still work
How does resistance vary within a thermistor?
+As the temperature increases, the current through the thermistor increases as the resistance decreases
+Keep the potential difference supply constant, gradually heat the thermistor [by placing thermistor against a beaker of hot water]
+You will find…
What prevents current surges and its effects?
The earth wire and a fuse are included in electrical appliances to prevent this from happening
What does the power rating tell you?
+This tells you the maxium amount of energy transferred between stores per second when the appliance is in use
Why does a resistor heat up when a current flows through it?
+Electrons collide with the ions in the lattice that make up the resistor as they flow through it.
+This gives the ions energy, which causes them to vibrate and heat up.
+The more the ions vibrate, the harder it is for electrons to get through the resistor [because there are more collisions]. This means that for a given p.d the current decreases as the resistor heats up.
+If the resistor gets too hot, no current will be able to flow. [Exception: The resistance of a thermistor decreases with an increase in temperature.
What is the process of the standard test circuit?
Non-linear graph
Show how the I-V graph for a filament lamp looks like:
What happens as current flows round a circuit?
+ The charges transfer energy as they struggle against resistance
What happens when an electrical charge flows through a component
- It has to do work against resistance
- This causes an electrical transfer of energy [work done = energy transferred]
What are I-V graphs
+Current - potential difference graphs
+This shows how the current varies as you change the potential difference
What is potential difference?
+The driving force that pushes the charge round
+The energy change per unit of charge between two points
+Unit, volt [V]
What is the Battery supply?
D.C
What is one volt also known as?
One joule per coulomb
What is the formula for power?
What colour is the earth wire
Green and yellow
Where is energy supplied in a circuit?
+Energy is supplied to the charge at the power source to ‘raise’ it through a potential
+The charge gives up this energy when it ‘falls’ through any potential drop in components elsewhere in the circuit [eg. resistors]
What does it mean when atoms are neutral
Number of protons = Number of electrons
What is mains supply?
A.C
What does total charge depend on?
Current and time
Where is all the mass of an atom located?
In the nucleus +The nucleus is tiny [about 10,000 times smaller than the whole atom]
What is current caused by in metals?
+By a flow of electrons
What does the earth wire do?
+This wire is for safety and protecting the wiring.
+It carries the current away if something goes wrong and stops the appliance casing becoming live
+It’s also at 0V
What does it mean if an atom gains or loses an electron?
- If an atom gains an electron, it becomes a negative ion
- If an atom loses an electron, it becomes a positive ion.