Current Electricity - Drift velocity

Which of the following characteristics of electrons determines the current in a conductor?

• A. Drift velocity alone

• B. Thermal velocity alone

• C. Both A and B

• D. Neither A nor B

In the equation I = nAvq, what does v represent?

• The speed of the electrons

• The average speed of the electrons

• The velocity of the electrons

• The average velocity of the electrons

• the fastest speed of all electrons

If the current in a specific copper wire increases this can be due to _____________________.

• An increase in the charge carrier density

• An increase in the electron drift speed

• An increase in its cross sectional area

• An increase in the charge of electrons

If the current at a given point in a circuit is 2.5 Amp, then how many electrons pass that point on the circuit in a time period of 1 minute.

Answer:

• 9.375 x 10²⁰ electrons

• 9.375 x 10²¹ electrons

• 9.375 x 10¹⁹ electrons

• 9.375 x 10¹⁸ electrons

A conductor of cross-sectional area 0.10  $mm^2$  carries a current of 2.5 A. If the number of conduction electrons per cubic metre is  $1.0\times10^{28\ }$   $m^{-3}$  . What is the value of drift velocity of the free electrons in the conductor?

• 1.6 $\times10^{-2}\ m\ s^{-1}$  

• 3.9 $\times10^{-2}\ m\ s^{-1}$  

• 3.0 $\times10^{-3\ }m\ s^{-1}$  

• 6.2 $\times10^{-3\ }m\ s^{-1}$  

 A conductor of length 2.0 m and cross-sectional area 5.0 $\times10^{-6}\ m^2$  carries a current of 6.0 A. If the drift velocity of the conduction electrons is 1.5 $\times10^{-4}\ m\ s^{-1}$ , what is the number of electrons in the conductor?

• 2.5 $\times10^{23}$  

• 2.9 $\times10^{23}$  

• 4.2 $\times10^{23}$  

• 5.0 $\times10^{23}$  

A tungsten wire of length 1.00 m and cross-sectional area 2.01 $\times10^{-6}\ m^2$  carries a current of 5.00 A. If the number of free electrons per unit volume is 4.3 $\times10^{28}$  , what is the time taken by an electron to travel from one end of the wire to the other end?

• 1.81 $\times10^3$  s

• 2.77 $\times10^3$  s

• 4.51 $\times10^3$  s

• 7.25 $\times10^3$  s

A current flows in a copper wire. The current density in the wire is 1.4 $\times10^6A\ m^{-2}$ . If the number of free electrons in 1 $m^3$  of wire is 8.4 $\times10^{28}$ , what is the drift velocity of the electrons? 

• 1.04 $\times10^{-4}m\ s^{-1}$  

• 3.10 $\times10^{-4}m\ s^{-1}$  

• 1.67 $\times10^{-3}m\ s^{-1}$  

• 1.90 $\times10^{-3}m\ s^{-1}$  

In the equation I=nAvq, which option(s) describe the meaning of n?

• the charge carrier density

• the number of charge carriers per unit volume

• the number of charge carriers per m³

• the number of charge carriers in the wires

• the total charge carriers available in the battery

When a thick wire is connected in series with a thin wire of the same material which of the below is/are true?

• The current through the thick wire is greater than the current through the thin wire

• The electrons move slower through the thin wire than through the thick wire

• The number of charge carriers per unit volume is greater in the thick wire than in the thin wire

• The number of charges flowing per second past a cross section of the thick wire is the same as that flowing past a cross section of the thin wire