CIRCUITS

In a series circuit with two identical bulbs, what happens to the remaining bulb when one is replaced with a wire?

The remaining bulb gets brighter. Subtracting bulbs from a series circuit decreases the resistance, thus increasing the current and brightness.

A cell's membrane thickness doubles but the cell stays the same size. Part A How do the resistance and the capacitance of the cell membrane change?

The resistance increases, the capacitance decreases

What happens to the current supplied by the battery when you add an identical bulb in parallel to the original bulb?

current doubles

Four resistors (R1 = 150 Ω, R2 = 250 Ω, R3 = 350 Ω, R4 = 450 Ω) are connected in series with a 12-V battery. What is the current that flows through the 250-Ω resistor?

10.0 mA For resistors in series, the equivalent resistance is Req=R1+R2+R3+R4=150 Ω+250 Ω+350 Ω+450 Ω=1200 Ω. The current through all of the resistors, and therefore through the 250-Ω resistor, is I=ΔV/R_eq =12 V/1200 Ω =0.010 A = 10.0 mA.

Rank in order, from brightest to dimmest, the identical bulbs A, B, and C.

A, (BC)

1) Rank the three identical bulbs from brightest to dimmest. 2) Suppose a wire is connected between points 1 and 2. What happens to bulb A? B? C?

A, (BC) gets brighter; out; out

In a series circuit of two resistors, the resistors have the same __________; in a parallel circuit of two resistors, the resistors have the same __________

Current through them, voltage across them

When three resistors are combined in series, the total resistance of the combination is __________.

greater than any of the individual resistance values

When three resistors are combined in parallel, the total resistance of the combination is __________.

less than any of the individual resistance values

You have a collection of 1.0 kΩ resistors. How can you connect four of them to produce an equivalent resistance of 0.25 kΩ? 2 parallel and 2 parallel and all it in series 2 in series and 2 in series and all it in parallel all in parallel all in series

all in parallel

Four resistors (R1 = 150 Ω, R2 = 250 Ω, R3 = 350 Ω, R4 = 450 Ω) are connected in parallel with a 12-V battery. What is the equivalent resistance of the circuit?

63.5 To find the equivalent resistance of resistors in parallel, use 1/R_eq=1/R1 + 1/R2 + 1/R3 + 1/R4. The equivalent capacitance for this circuit is Req=(1/150 Ω + 1/250 Ω + 1/350 Ω + 1/450 Ω)^−1 =63.5 Ω.

Four resistors (R1 = 150 Ω, R2 = 250 Ω, R3 = 350 Ω, R4 = 450 Ω) are connected in parallel with a 12-V battery. What is the total current drawn in this circuit?

=189 mA The current drawn in this circuit is I=ΔV/Req, where Req is 63.5 Ω for these four resistors in parallel. So the current is I=12 V / 63.5 Ω =189 mA.

A defibrillator is designed to pass a large current through a patient's torso in order to stop dangerous heart rhythms. Its key part is a capacitor that is charged to a high voltage. The patient's torso plays the role of a resistor in an RC circuit. When a switch is closed, the capacitor discharges through the patient's torso. A jolt from a defibrillator is intended to be intense and rapid; the maximum current is very large, so the capacitor discharges quickly. This rapid pulse depolarizes the heart, stopping all electrical activity. This allows the heart's internal nerve circuitry to reestablish a healthy rhythm. A typical defibrillator has a 31 μF capacitor charged to 5000 V . The electrodes connected to the patient are coated with a conducting gel that reduces the resistance of the skin to where the effective resistance of the patient's torso is 100 Ω . 1) Which pair of graphs in the figure best represents the capacitor voltage and the current through the torso as a function of time after the switch is closed? 2) For the values noted in the passage above, what is the time constant for the discharge of the capacitor? 3) If a patient receives a series of jolts, the resistance of the torso may increase. How does such a change affect the initial current and the time constant of subsequent jolts? 4) In some cases, the defibrillator may be charged to a lower voltage. How will this affect the time constant of the discharge?

1) a 2)3.1 ms 3)The initial current decreases, the time constant increases 4)The initial current decreases, the time constant increases

There is a current of 0.25 A in the circuit ' 1) What is the direction of the current? Select the correct answer and explanation. 2) What is the value of the resistance R? 3) What is the power dissipated by R? 4)....

1)The direction of the current is counterclockwise because the batteries in this circuit are oriented to "oppose" each other and the 12 V battery "wins". 2)R = 6 Ω 3)

circuit w battery 15V, and two resistors in series (10 Ω & 20 Ω) 1) What is the potential difference across the 10 Ω resistor? 2)... 20Ω? 3)Choose the correct graph of the potential as a function of the distance s traveled through the circuit, traveling clockwise from V = 0 V at the lower left corner.

1)ΔV10 = 5.0 V 2) 10 V