P2 Flashcards
What does a switch look like?
Line. Circle. Line. Circle. Line.
What does a cell look like?
Line. Big vertical line. Gap. Small vertical line. Line.
What does a battery look like?
Line. Big vertical line. Gap. Small vertical line. (repeat) Line.
What does a lamp look like?
Line. Circle with an X in it. Line.
What does a fuse look like?
Line. Rectangle with line in it. Line.
What does a voltmeter look like?
Line. Circle with a V. Line.
What does an ammeter look like?
Line. Circle with an A. Line.
What does a diode look like?
Line. Circle with a skip symbol with a line through it. Line.
What does a thermistor look like?
Line. Rectangle with golf club in it. Line.
What does a resistor look like?
Line. Rectangle. Line.
What does a variable resistor look like?
Line. Rectangle with an arrow going from bottom left to top right. Line.
What does an LDR look like?
Line. Circle with a rectangle inside with 2 arrows outside pointing towards circle. Line.
What does an LED look like?
Line. Circle with a skip button and 2 arrows in right hand corner pointing away. Line.
What is current?
Flow of electrical charge.
What is the unit for current?
Amps (A)
What is needed for a current to flow?
A closed circuit with a potential difference.
What is potential difference?
Driving force that pushes the charge around the circuit.
Name the names and units for Q =I t
Charge in Coulombs. Current in Amps. Time in seconds.
Does the current change in different places in a circuit?
No. A current has the same value at any point in a single closed loop.
What is resistance?
Opposes the flow of charge.
The greater the resistance…
…the smaller the current that flows
Name the names and units for V =I R
Potential difference in Volts. Current in Amps. Resistance in ohms.
How do you connect the ammeter?
In series (normal).
How do you connect the voltmeter?
In parallel (in branches).
Required practical activity 3: Use circuit diagrams to set up and check appropriate circuits to investigate the factors affecting the resistance of electrical circuits. (6)
- Cut the wire into different lengths (e.g. 10 cm / 20 cm / 30 cm / 40 cm and 50 cm). 2. Attach one end of the wire to the positive bit of the power supply and the other end to the negative terminal using crocodile clips. 3. Record the length of the wire used and the readings of current (I) from the ammeter and potential difference (V) from the voltmeter. 4. Calculate the resistance (R) of the wire using Ohm’s Law (R = V / I). 5. Repeat the experiment with each wire length at least three times to ensure accuracy and consistency of results. 6. Plot a graph of wire length (x-axis) against resistance (y-axis) to observe any patterns (straight line)
What happens in series circuits? (3)
- Same current through each component. 2. The total potential difference of the power supply is shared between the components. 3. The total resistance of two components is the sum of the resistance of each component.
What happens in parallel circuits? (3)
- The potential difference across each component is the same. 2. The total current through the whole circuit is the sum of the currents through the separate components. 3. The total resistance of two resistors is less than the resistance of the smallest individual resistor.
What type of current is the mains?
AC
What is the frequency and potential different of the mains?
50 Hz and 230 V
What’s the difference between alternating and direct current?
AC flows in both directions whereas DC only flows in one direction.
What colour is the live wire and what does it do?
Brown - carries the alternating potential difference from the supply.
What colour is the neutral wire and what does it do?
Blue - completes the circuit.
What colour is the earth wire and what does it do?
Green and yellow stripes - safety wire to stop the appliance becoming live.
Why might a live wire still be dangerous even when a switch in the mains circuit is open?
Because there might not be a current in the live wire, but there will still be a potential difference in it. When you touch a live wire, current flows through your body and causes an electric shock.
What’s the pd between live and earth wire?
230 V
Name the names and units for P =V I
Power in watts = potential difference in volts x current in amps.
Name the names and units for P = I² R
Power in watts = current in amps squared x resistance in ohms.
Name the names and units for E =P t
Energy transferred in joules. Power in watts. Time in seconds.
Name the names and units for E =Q V
Energy transferred in joules. Charge in coulombs. Potential difference in volts.
What is the national grid?
The National Grid is a system of cables and transformers linking power stations to consumers.
How does the national grid work?
- Step up transformer increases voltage to 400,000 V and current decreases. 2. Step down transformer reduces voltage to 230 V.
Step up transformer has more turns with coils in…
Secondary
Step down transformer has more turns in..
Primary
What do you add to the transformers which joins the coils?
Iron core.
Why is the national grid efficient?
Cheap to have a high pd. Reduces energy loss.
What happens when certain insulating materials are rubbed against each other?
One loses electrons and becomes positive charged. The other gains electrons and becomes negative charged.
What happens when 2 electrically charged objects are brought close together?
They exert a force on each other.
How does the production of static electricity work?
- As electric charge builds, pd between object and earth increases from 0V. 2. If it’s large enough, electrons can cross the gap - this is the spark.
How to test attraction and repulsion?
Suspend a rod with a known charge and put other charges underneath. The same charge should repel whereas the opposite should attract.
What does a charged object create?
A charged object creates an electric field around itself. The electric field is strongest close to the charged object. The further away from the charged object, the weaker the field.
How can you show electric field?
Field lines.
