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Exam 18: Direct-Current Circuits

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Question 21

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A battery has an internal resistance R_int.Connecting a wire of negligible resistance between the terminals of the battery draws the maximum current I​_max from this battery.If instead a resistor is connected between the terminals,a smaller current is produced.What value resistor placed across the terminals would result in the current produced to be half of I​_max?

A) 0.63R_int
B) R_int
C) 0.50R_int
D) 0.37R_int

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Question 22

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If one doubles the emfs in a circuit and doubles the resistances in the circuit at the same time,what happens to the currents through the resistors? Assume there are only emfs and resistors in the circuit.

A) They stay the same.
B) They double.
C) They quadruple.
D) They halve.

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Question 23

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Two resistors of values 6.0 and 14.0 Ω are connected in parallel.This combination in turn is hooked in series with a 2.0-Ω resistor.What is the overall resistance of this combination?

A circuit contains a 6.0-V battery,a 4.0-Ω resistor,a 0.60-µF capacitor,an ammeter,and a switch in series.What will be the charge on the capacitor 10 min after the switch is closed?

Household 120-V outlets are made to accept three-pronged plugs.One of the prongs attaches to the "live" wire at 120 V,and another attaches to the "neutral" wire that is connected to ground.What is the round third prong for?

Which two resistors are in parallel with each other?

A 1 000-V battery,a 3 000-Ω resistor and a 0.50-µF capacitor are connected in series with a switch.The time constant for such a circuit,designated by the Greek letter,τ,is defined as the time required to charge the capacitor to 63% of its capacity after the switch is closed.What is the value of τ for this circuit?

A series RC circuit has a time constant of 0.900 s. The battery has an emf of 24.0 V, and the maximum current in the circuit is 0.500 mA. -What is the charge stored in the capacitor 2.00 s after the switch is closed?

If ε = 20 V,at what rate is thermal energy being generated in the 20-Ω resistor?

What is the current through the 2.0-Ω resistor?

When a 35.0-Ω resistor is connected across a 4.50-V battery,a current of 500 mA flows.What is the power output delivered by the emf of the battery?

In order for a circuit to respond quickly,its time constant should be short.In a circuit involving resistance and capacitance,which of the following choices would result in the shortest time constant?

Three resistors,with values of 1.0,4.0,and 10.0 Ω,respectively,are connected in series.What is the overall resistance of this combination?

A battery has an emf of 12.0 V and an internal resistance of 3.00 Ω.If the battery delivers 120 mA when connected to a load,what is the load resistance?

Three resistors with values of R₁,R₂ and R₃,respectively,are connected in series.Which of the following expresses the total resistance,R_T,of the three resistors?

An RC circuit with resistance R​₀ and capacitance C​₀ has a time constant τ​₀.Which of the following additions to the circuit would result in the time constant doubling?

Two resistors of values 7.0 and 15.0 Ω are connected in parallel.This combination in turn is hooked in series with a 3.8-Ω resistor and a 22.3-V battery.What is the current in the 3.8-Ω resistor?

A series combination of a 48.0- $\mu$ F capacitor and a resistor are connected to a 12-V battery.After one second,the voltage across the capacitor is 10 V.What is the resistance of the resistor?

A series RC circuit,which is made from a battery,a switch,a resistor,and a 3.45-μF capacitor,has a time constant of 11.0 ms.If an additional 12.0-μF is added in series to the 3.45-μF capacitor,what is the resulting time constant?

A hair dryer draws 1 350 W,a curling iron draws 700 W,and an electric light fixture draws 550 W.If all three of these appliances are operating in parallel on a 120-V circuit,what is the total current drawn?