Electricity: Electrical Resistance Flashcards
What happens to a metal wire at a constant temperature when the voltage across it is varied?
The resistance does not change.
How can you investigate the resistance of a component?
Connecting it to a power supply with an ammeter in series with it and a voltmeter parallel with it.
What is ohms law?
When the current and voltage are proportional.
How will a component of low resistance appear on a current-voltage graph?
The gradient will be steeper (closer to the ground)
What happens to the resistance of a filament bulb as the voltage is raised?
It increases because the filament temperature increases substantially so it’s atoms will vibrate faster, this makes it harder for a current to flow.
What happens to the resistance of a silicon diode as the voltage is raised?
It drops so as the voltage increases the current will become successfully larger.
What happens to the resistance of a LDR as the voltage is raised?
In dark conditions LDRs contain few free electrons and so have a high resistance. However when light is shone on the electrons are freed and the resistance decreases. This is because it is made from semiconducting material.
What happens to the resistance of a thermistor as the voltage is raised?
At room temperature the number of free electrons is small so the resistance is large. When it is warmed the number of free electrons increases and the resistance decreases.
What is a resistor?
A component designed to control the current flowing in a circuit. A low resistance means a high current and vice-versa.
How can you indicate the presence of current in a circuit?
Use a lamp or LED and see if it turns on.
What is the relationship between voltage, current and resistance?
Voltage = current*resistance or V = I*R.
