Exam 21: Electric Current and Direct-Current Circuits

A capacitor C is connected in series with a resistor R across a battery and an open switch.If a second capacitor of capacitance 2C is connected in parallel with the first one,the time constant of the new RC circuit will be

A certain metal has a resistivity of 1.68 × 10^-8 Ω ∙ m.You have a long spool of wire made from this metal.If this wire has a diameter of 0.15 mm,how long should you cut a segment so its resistance will be 15 Ω?

A number of resistors are connected across points A and B as shown in the figure.What is the equivalent resistance between points A and B?

If the power rating of a 400-Ω resistor is 0.80 W,what is the maximum current it can safely draw?

A device with a resistance of Is connected to a Battery.How much power does the device use?

Four unequal resistors are connected in series with each other.Which one of the following statements is correct about this combination?

Determine the current in the 7.0-Ω resistor for the circuit shown in the figure.Assume that the batteries are ideal and that all numbers are accurate to two significant figures.

A 5-µF,a 7-µF,and an unknown capacitor C_X are connected in series between points a and b.What do you know about the equivalent capacitance C_ab between a and b? (There could be more than one correct choice. )

Three resistors with resistances of 2.0 Ω,6.0 Ω,and 12 Ω are connected across an ideal dc voltage source V = 2.0 V,as shown in the figure.What is the total current I in this circuit?

Three capacitors of equal capacitance are arranged as shown in the figure,with a voltage source across the combination.If the voltage drop across C₁ is 10.0 V What is the voltage drop across C₃ ?

A 2.0-Ω resistor is in series with a parallel combination of 4.0-Ω,6.0-Ω,and 12-Ω resistors.What is the equivalent resistance of this system?

When unequal resistors are connected in parallel in a circuit,

Two 4.0-Ω resistors are connected in parallel,and this combination is connected in series with 3.0 Ω.What is the equivalent resistance of this system?

A 3.0-Ω resistor is connected in parallel with a 6.0-Ω resistor.This combination is then connected in series with a 4.0-Ω resistor.The resistors are connected across an ideal 12-volt battery.How much power is dissipated in the 3.0-Ω resistor?

The capacitive network shown in the figure is assembled with initially uncharged capacitors.Assume that all the quantities in the figure are accurate to two significant figures.The switch S in the network is kept open throughout.What is the total energy stored in the seven capacitors?

For the graph shown in the figure,what physical quantity does the slope of the graph represent for a dc circuit?

A 1.0-mm diameter extension cord is made of metal having a resistivity of 1.68 × 10^-8 Ω ∙ m.When it carries a current of 15 A,what is the potential difference between two points in the cord that are 100 m apart?

What is the resistance of a cylindrical metal rod 1.0 cm in diameter and 45 m long,if the resistivity of the metal is 1.4 × 10^-8 Ω ∙ m?

A light bulb operating at a dc voltage of 120 V has a resistance of 200 Ω.How much power is dissipated in this bulb?

Four resistors having resistances of 20 Ω,40 Ω,60 Ω,and 80 Ω are connected in series across an ideal 50-V dc source.What is the current through each resistor?