Resistance Flashcards
Equation linking resistance, voltage and current
V=IR
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Investigating resistance practical
1. Equipment: a…, c…, w…, c… c…, m… r…, b…, t… w…
2. Always … the ammeter in … and the voltmeter in …
3. Attach a … clip to the … level with …cm on the …
4. Attach the … crocodile … to the wire …cm away from the … clip, and … down the … of the wire … the …
5. … the switch then … the … and the …
6. Open the … then move the … crocodile clip another …cm along the …, and close the … again and record the new … and …
7. … this for several … lengths on the … wire
8. Use your recording to … the … using V=….
9. Plot a … with … on the y axis and … … on the x axis and draw on a … of … fit
10. … should be a … line directly through the …, meaning … in … proportional to the … of the wire
- Equipment: ammeter, voltmeter, wires, crocodile clips, meter ruler, battery, test wire
- Always connect the ammeter in series and the voltmeter in parallel
- Attach a crocodile clip to the wire level with 0cm on the ruler
- Attach the second crocodile clip to the wire 10cm away from the first clip, and write down the length of the wire between the clips
- Close the switch then record the current and the voltage
- Open the switch then move the second crocodile clip another 10cm along the wire, and close the switch again and encore the new current and pd
- Repeat this for several different lengths on the test wire
- Use your recording to calculate the resistance using V=IR
- Plot a graph with resistance on the y axis and wire length on the x axis and draw on a line of best fit
- Graph should be a straight line directly through the origin, meaning resistance in directly proportional to the length of the wire
What is an ohmic conductor
A conductor with a resistance that is constant at a constant temp, eg a wire, resistor
What doesn’t chance with current in an ohmic conductor
Resistance
In an ohmic conductor what is directly proportional to the potential difference
The current, V=IR
What happens when electric charge flows through a filament lamp
-It … some … to the … energy … of the … which … up
-resistance … with … so current …
-the … lamp … up more and the resistance …
-It transfers some energy to the thermal energy store of the filament which heats up
-resistance increases with temperature so current increases
-the filament lamp heats up more and the resistance increases
In diodes what does resistance depend on
The direction of the current, they let current flow in one direction but have a very high resistance if reversed
What is an I-V characteristic graph
A graph of current against potential difference fit a component
Linear components have an I-V characteristic that’s a …
Straight line
Examples of linear components that have an I-V characteristic with a straight line
Ohmic conductor
Non-linear components have a …. I-V characteristic
Curved
Examples of non-linear components with a curved I-V characteristic graph
Filament lamp, diodes
How a filament lamp works- graph
-as the … increase the temp of the filament …, so the resistance …
-this means less … can … per unit … so the graph gets …
-as the current increase the temp of the filament increases, so the resistance increases
-this means less current can flow per unit pd so the graph gets shallower
How an ohmic conductor works -graph
-the current is directly proportional to the potential difference so you get a straight line
How a diode works- graph
-current will only flow through a diode in one direction
-the diode has a very high resistance in the reverse direction so does not cross the x axis
