Electric Current

The diagram shows the symbol for a wire carrying a current I. What does this current represent?

• the amount of charge flowing past a point in XY per second

• the number of electrons flowing past a point in XY per second

• the number of positive ions flowing past a point in XY per second

• the number of protons flowing past a point in XY per second

When there is no current in a wire, which statement about the conduction electrons in that wire is correct?

• electrons in the wire are moving totally randomly within the wire

• equal numbers of electrons move at the same speed, but in opposite directions, along the wire

• no current is flowing therefore the electrons in the wire are stationary

• no current is flowing therefore the electrons in the wire are vibrating around a f point

When will 1 C of charge pass a point in an electrical circuit?

• when 1 A moves through a potential difference of 1 V

• when a power of 1 W is used for 1 s

• when the current is 5 mA for 200 s

• when the current is 10 A for 10 s

There is a current of 10 mA in a conductor for half an hour. How much charge passes a point in the conductor in this time?

• 0.3 C

• 5 C

• 18 C

• 300 C

An ammeter shows a reading of 20 mA. How many electrons flow through the ammeter in 10 seconds ?

• 0.20

• 3.2 x 10²⁰

• 200

• 1.3 x 10¹⁸

The current I in a conductor is given by the equation shown.

I = Anvq

What does the letter n represent in this equation?

• charge carried per charge carrier

• number of charge carriers per unit area

• number of charge carriers per unit volume

• total mass of charge carriers per unit volumetotal mass of charge carriers per unit volume

A copper wire of cross-sectional area 2.0 mm² carries a current of 10 A. How many electrons pass through a given cross-section of the wire in one second?

A 6 A current flows in a wire with has 8.2 × 10²⁸ electrons pass through it at an average drift speed of 0.09 mm/s . What is the cross-sectional area of the wire?

• 0.14 mm²

• 5.1 mm²

A fine mist of oil droplets is sprayed into air. As the oil droplets leave the nozzle of the spraying device they can become electrically charged.

What is not a possible value for the charge on an oil droplet?

• zero

• 1.0 x 10^-19 C

• 4.8 x 10^-19 C

• 8.0 x 10^-19 C

What could not be used to create an electric current?

• proton