20) Basics of Electricity Flashcards
State what is meant by superconductivity and explain the required conditions for a material to become superconducting.
- Superconductivity means a material has zero resistance.
- Resistivity decreases with temperature.
- Becomes superconducting when you reach the critical temperature.
Explain what is meant by the emf of a battery.
Work done by a battery per unit charge.
Explain what is meant by the internal resistance of a battery.
The resistance of the materials within the battery.
Describe the procedure the student would follow in order to obtain an I-V curve for a semiconductor diode.
- Connect circuit up.
- Measure current (I) and voltage (V).
- Vary resistance/voltage.
- Obtain a range of results.
- Reverse connections to the power supply and repeat.
- Plot a graph of pd against current.
- Change range on meters when doing reverse bias.
Explain what is meant by critical temperature.
The temperature at which a material becomes a superconductor.
State and explain one reason why it is an advantage for a rechargeable battery to have a low internal resistance.
- Less energy wasted with lower internal resistance.
- Charges quicker.
State what is meant by an ohmic conductor.
A component with constant resistance.
Give two uses of a superconductor.
- Powerful magnets.
- Bullet train.
State and explain why it is important for car batteries to have a very low internal resistance.
- Need a large current to start the car.
- Internal resistance limits the current and increases lost volts.
State what happens to the resistance of the filament lamp as the current increases.
Resistance of filament lamp increases.
State and explain whether a filament lamp is an ohmic or non-ohmic conductor up to its working power.
Filament lamp is a non-ohmic conductor as the current is not directly proportional to the voltage.
Explain why an oscilloscope would show a bright spot rather than a horizontal line.
-Time base is switched off.
Explain, in terms of electron motion, why the I–V characteristic for the filament lamp is a curve.
-An increase in current leads to an increase in
temperature.
This causes an increase in the movement of atoms.
-And therefore an increase in the rate of collisions with
electrons.
So the resistance increases as shown by V not proportional to I.
Explain what is meant by a potential divider.
A combination of resistors in series connected across a voltage source to produce a required pd.
