(AP C EM) Quiz 5.1

A 9 V battery is connected to a 450  $\Omega$  load. If the internal resistance of the battery is negligible, how long will it take for 2 C to pass through the load

• 0.01 s

• 0.02 s

• 25 s

• 50 s

• 100 s

A circuit contains a length of tungsten wire with resistance
 $R$  . An increase in the resistance would result if which of the following could be decreased?

• The resistivity of the tungsten

• The cross-sectional area of the wire

• The length of the wire

• The temperature of the wire

• The current in the wire

A 30-ohm resistor and a 60-ohm resistor are connected as shown in the figure to a battery of emf 20-volts and internal resistance  $r$  . The current in the circuit is 0.8-ampere. What is the value of  $r$  ?

•  $0.22\ \Omega$  

•  $4.5\ \Omega$  

•  $5.0\ \Omega$  

•  $16\ \Omega$  

•  $70\ \Omega$  

A copper wire of length  $L$  and diameter  $D$  dissipates energy at a rate  $P_0$  when the current in the wire is 10 A. A second copper wire of length  $L$   has diameter  $2D$  . What current in the second wire would dissipate energy at a rate  $P_0$  ?

• 2.5 A

• 5.0 A

• 10 A

• 20 A

• 40 A

A hair dryer is rated as 1200 W, 120 V. Its effective internal resistance is

• $0.1\ \Omega$
  

• $10\ \Omega$

• $12\ \Omega$

• $120\ \Omega$

• $1440\ \Omega$

A rectangular resistor of length 10 cm and cross-sectional area 8.0 cm2 is connected to a battery as shown in the figure. The resistor draws a current density equal to 2500 A/m2. If the resistivity of the resistor is  $0.048\ \Omega\text{m}$  , what is the potential difference of the battery?

•  $2\times10^{-6}\ \text{V}$  

•  $12\ \text{V}$  

•  $120\ \text{V}$  

•  $1200\ \text{V}$  

•  $5200\ \text{V}\$  

A narrow beam of protons produces a current of  $1.6\times10^{-3}\ \text{A}$  . There are  $10^9$  protons in each meter along the beam. Of the following, which is the best estimate of the average speed of the protons in the beam?

•  $10^{-15}\ \text{m/s}$  

•  $10^{-12}\ \text{m/s}$  

•  $10^{-7}\ \text{m/s}$  

•  $10^7\ \text{m/s}$  

•  $10^{12}\ \text{m/s}$  

For the circuit shown, the resistor is connected to an ideal 12 V battery and is made of material with a resistivity of  $640\ \Omega\text{m}$  . The current in the circuit is most nearly

• 0.60 mA

• 3.8 mA

• 19 mA

• 94 mA

• 1600 mA

A  $4.0\ \Omega$  resistor is constructed using a wire diameter of 1.0 mm and a resistivity of  $1.68\times10^{-8}\ \Omega\text{m}$  . The length of wire used to create the resistor is most nearly 

• 2340 m

• 750 m

• 240 m

• 190 m

• 60 m

The current in a  $10\ \Omega$  resistor is given as a function of time  $t$  by the equation  $I=I_0e^{-\alpha t}$  where  $I_0=4\ \text{A}$  and  $\alpha=2\ \text{s}^{-1}$  . What is the total energy dissipated in the resistor from time  $t=0$  until the current becomes zero?

• 20 J

• 40 J

• 80 J

• 160 J

• 320 J