Electric Current - exam practice
Electric Current
Question 1 of 6
An electric kettle has a 600 W heating element.
The heating element has a cross-sectional area of 5.03 x 10-6 m2.
The number density of charge carriers in the heating element is 7.9 x 1028 m-3.
The current through the heating element is 3 A.
Calculate the resistance of the heating element.
Calculate the number N of electrons passing through the heater in 3 minutes.
Calculate the mean drift velocity v of the electrons in the heating element.
This question is about Kirchoff's laws.
State Kirchoff's first law.
State the value of the current at P.
The wire at P has a radius of 0.4 mm. The number density of charge carriers in the wire is 8.49 x 1028.
Calculate the mean drift velocity of electrons in the wire at P.
The diagram below shows a battery connected across a light dependent resistor.
State the reading on the voltmeter.
The light intensity incident on the LDR is increased.
Describe and explain the effect on the ammeter and voltmeter readings.
The LDR has a resistance of 450 .
The number density of charge carriers is 7.5 x 1028 m-3 and the cross sectional area is 3.2 x 10-6.
Calculate the mean drift velocity of electrons in the LDR.
This question is about the electric current flowing in a circuit.
Define electric current.
State the name of the charge carrier in electrical circuits containing wires.
State the S.I unit for charge.
Calculate the number of electrons that pass point P in 2 minutes.
The drift velocity of the electrons at point P is 0.2 mm s-1. The wire has a diameter of 1.2 mm.
Calculate the number density of charge carriers in the wire.
This question is about electric current.
State the name of the charge carrier responsible for electric current in a metal.
An aluminium rod has a radius of 7 mm and a potential difference of 12 V applied across it.
120 C travels along the rod in 40 s.
Calculate the current in the rod.
The mean drift velocity of electrons in the wire is 8.09 m s-1.
Calculate the number density of electrons in the aluminium rod.
The aluminium rod is connected to a second rod with twice the diameter.
State the relationship between the current entering the aluminium rod and the current leaving the second aluminium rod.
The second rod is also made from aluminium.
Calculate the mean drift velocity of electrons in the second rod.
This question is about electric currents in circuits.
Define drift velocity of charge carriers in a conductor.
The current in a copper wire of cross-sectional area 2 mm2 is 5 A.
The number density of electrons is 8.5 x 1028 m-3.
Calculate the drift velocity of the electrons in the wire.
Explain why the drift velocity of electrons in a conductor is so slow.
Calculate the number of electrons that flow through the wire in part b) in 1 minute.