circuits Flashcards
what is static electricity?
when charges on objects cannot move.
what happens when two insulators are rubbed together?
due to the frictional force, one of the insulators will lose electrons and one will gain electrons; this gives them static electricity which make them attract to each other slightly.
In a battery what direction do electrons move in?
from the negative to the positive.
What is current?
current is the rate of electrons passing a point per second measured in amps (A) by a ammeter.
What formula relates current, time and charge?
charge (C)= current (A) x time (secs)
What components makes a complete circuit?
-a electron source (battery)
-a conductor (wire)
-a component (eg bulb)
What factors change the resistance of a wire?
-type of material
-length of wire
-diameter of wire
-temperature
What is resistance?
resistance is the force that pushes a current through a conductor in the opposite direction of its flow measured in Ohms (Ω) by a ohmmeter.
Describe how resistance is affected when a wire…
-increases in temperature
-is made longer
-is made thicker
-an increase in temperature increases, the resistance increases in a wire as more kinetic energy is given to the electrons, this makes them collide with the walls of the wire more frequently, making it harder for them to travel through a wire.
-if a wire is made longer, the resistance increases.
-if a wire is made thicker, the resistance decreases since the atoms within it are less compressed.
What formula links voltage, current and resistance?
voltage (V) = current (A) x resistance (Ω)
What is voltage?
Voltage (potential difference) is the amount of pressure it takes to push a current through a wire.
What is Ohm’s law?
that the current in a circuit at a constant temperature is directly proportional to the voltage.
What happens in terms of Ohm’s law if a circuit increases in temperature?
since the circuit is not at a constant temperature, resistance increases, meaning that the current is no longer directly proportional to the voltage.
Explain the experiment you would need to carry out to investigate how factors (length) change the resistance of a wire: (6)
-first attach a power pack to an ammeter in series with a wire.
-attach the other end of the power pack and the ammeter to a long wire using two wires and crocodile clips .
-at other end of the wire attach a voltmeter in parallel to the circuit.
-using a meter ruler, use crocodile clips to adjust the length of the wire at set intervals such as 10cm, 20cm, etc.
-at one length interval, turn on the power pack and record the current and voltage. Repeat this 3 times at least.
-then at the next interval record the current and voltage, repeating process of first interval.
-to avoid the wire from overheating, turn off power pack as you prepare next steps.
-using the formula voltage/current calculate the resistance.
-plot graph
