Section 7- Electricity And Cicruits Flashcards
What’s the current ?
What’s current measured in?
-flow of electric charge around a Cicruit
-amps
What’s potential difference?
What else is potential difference called?
Unit?
-the driving force that pushes the charge around
-voltage
-Volts
What’s resistance?
Unit for resistance
-Anything that slows the flow down
- ohm 🧲
Why will current flow through an electrical circuit?
- if there’s a potential difference
- if the circuit is closed (complete)
What does the current flowing through a component depend on?
Current flowing through a circuit Depends on the POTENTIAL DIFFERENCE and the RESISTANCE of the component
What happens to the current when there’s a higher potential difference ?
Higher current
Greater resistance = …. Current
Greater resistance = smaller current
How do currents move in metals?
-Metals are bonded in a lattice (positive ions surrounded by free electrons)
-these electrons are free to move through the metal
Do electrons move from positive—> negative or the other way around ?
Electrons move from positive to negative in a circuit
How is charge calculated?
Charge = current X time
How do you calculate potential difference using current and resistance ?
Potential difference = current X resistance
How do you calculate resistance?
Resistance = p.d /current
What does temperature increase along with?
Resistance
Why does resistance increase with temperature ?
Electrons collide with ions in the lattice that makes up the reuses or as they flow through it
Gives ions energy —-> causes them to vibrate more
The more the ions vibrate, the harder it is for electrons to get through a resistor as there are more collisions
2 types of circuits ..
Series circuits
Parallel circuits
What’s a series circuit?
All components are connected in a line
3 rules of a series circuit…
-The current is the same everywhere
-total potential difference of the supply is shared between components (pd of each component depends on its resistance)
-total resistance of circuit increases as you add resistors
Why are parallel circuits more useful?
If you remove or disconnect one of the parts, it will hardly effect anything at all
What happens to the potential difference across all the components in a parallel circuit?
All components get the full source of pd. all their pds will equal the full voltage supply
What happens to the current in parallel circuits?
The current is shared between branches
What does adding a resistor in a parallel curcuit do to resistance?
Decreases resistance
Why does adding a resistor in a parallel curcuit decrease the resistance?
By adding another loop, the current has more than one direction to flow in.
This increases the total current
By using V=IR, an increase in current means a decrease in total resistance for a circuit
What’s a series circuit?
Whats the current like in it?
Whats the potential difference like?
Whats the total resistance the sum off?
-Components all connected end to end.
-Current is the same everywhere
- potential difference is shared across the circtuit ( PD of supply = sum of PD across each component)
-total resistant is the sum of the resistance across each component
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What’s a parallel circuit ? What happens to the current on each branch ?what the voltage like on each branch ? Why will two resistors in parallel have a smaller overall resistance than just one ?
- blanched circuit
-current splits into multiple paths. Current of all branches adds to total current
-voltage is the same on each branch
- because the charge will go along another branch , it has other options
Equation for energy transfered…
E=QV
ENERGY TRANSFERRED = charge moved X potential difference
Where should current be measured on a circuit? How’s it measured? V=
-Anywhere
-measured with an ammeter placed in series
V= IR
How does resistance change current and temp and why?
W
Greater resistance makes it harder for the charge to flow through the component , therefore the currents smaller.
When electrons flow through revision, they collide with ions in the resistor. Current does work against resistance. This transfers energy to ions , making them vibrate more and making it difficult for current to flow through resistor. Same thing happens for temp
Equation to find voltage …
V=IR
Equation for charge ?
Q=IT
2 equations for power…
P=IV
Power= current X voltage
P= I^2 X R
Power= current ^2 X resistance
2 Equation’s for energy
E=PT
energy = power X time
E=QV
Energy = charge X voltage
How does resistance change when youincrease length ?why?
Greater length = more resistance , therefore lower current
- electrons need to make their way through more resistor ions, so it’s harder than if you use a short wire
How does resistance change with light in an LDR?
Greater intensity of light, lower resistance . So resistance greatest when dark
What is AC? Where does it come from ? What happens to the current
AC is alternating current, which comes from the mains
Current continuously varies from positive to negative
What’s DC? What’s the movement of charge like? Where does it come from?
Dc is direct current which is the movement of charge in one direction only
Supplied by cells and batteries
What Hz and V is the uk mains supply
50 Hz
230V
What are the 3 wires in a plug?
Live wire
Neutral wire
Earth wire
What’s live wire?
A brown wire that carries voltage from the mains to appliance
What’s neutral wire?
A blue wire that completes the circuit
What’s earth wire?whay it connected to?
-Green and yellow striped wire that acts as a safety wire to stop the appliance becoming live.
-The earth
What does the fuse do?How
The fuse is connected to the live wire. If a large current passes through the live wire, fuse heats up and melts , breaking the circuit
Prevents a fire
