1. A 50-W, 120-V bulb is connected in parallel with a 15-W, 120-V bulb. What is
ID: 1445091 • Letter: 1
Question
1. A 50-W, 120-V bulb is connected in parallel with a 15-W, 120-V bulb.
What is the net resistance?
Rnet = ______________
2. What would the current I1 be in (Figure 1) if the 12-? resistor is shorted out? Let r= 1.7 ? .
I1 = _________________
3. Suppose two batteries, with unequal emfs of 2.00 V and3.00 V, are connected as shown in (Figure 1) .
If each internal resistance is r = 0.250 ? , and R = 4.00 ?, what is the voltage across the resistor R?
VR = __________________
4. Suppose three parallel-plate capacitors, whose plates have areas A1, A2, and A3 and separations d1, d2, and d3, are connected in parallel.
Determine the equivalent capacitance of these capacitors.
Express your answer in terms of the variables A1, A2, A3, d1, d2, d3, and the electric constant ?0.
Ceq = ___________
5. Three 1.90-k? resistors can be connected together in four different ways, making combinations of series and/or parallel circuits.
What are these four ways?
Check all that apply.
a) What is the potential difference between points d and a in (Figure 1) ?
Vda = _____
b) What is the terminal voltage of 85-V battery?
Vterminal = ______
c) What is the terminal voltage of 45-V battery?
Vterminal = ______
7.How many 14 ? resistors must be connected in series to give an equivalent resistance to five 560 ? resistors connected in parallel?
n = ____________
8. Three 50-? lightbulbs and three 70-? lightbulbs are connected in series.
a) What is the total resistance of the circuit?
Rtotal = _______________
b) What is the total resistance if all six are wired in parallel?
Rtotal = _______________
9.Three equal resistors (R) are connected to a battery as shown in (Figure 1) .
a) Qualitatively, what happens to the voltage drop across each of these resistors when the switch S is opened, after having been closed for a long time?
b) Qualitatively, what happens to the current flow through each of these resistors when the switch S is opened, after having been closed for a long time?
c) What happens to the terminal voltage of the battery, when the switch S is opened, after having been closed for a long time?
d) If the emf of the battery is 9.0 V, what is its terminal voltage when the switch is closed if the internal resistance r is 0.60 ? and R=6.00??
V =___________
e) What is the terminal voltage when the switch is open?
V =___________
10. Determine the terminal voltage of each battery in the figure.(Figure 1)
a) Determine the terminal voltage of top battery.
b) Determine the terminal voltage of bottom battery.
Vterminal = ______________
11. Eight bulbs are connected in parallel to a 220 Vsource by two long leads of total resistance1.9 ? .
a) If 270 mA flows through each bulb, what is the resistance of each?
R =______
b) If 270 mA flows through each bulb, what fraction of the total power is wasted in the leads?
Pwasted/Ptotal = _____________
12. A circuit contains a single 230-pF capacitor hooked across a battery. It is desired to store four times as much energy in a combination of two capacitors by adding a single capacitor to this one.
a) How would you hook it up?
The capacitor must be connected in parallel to the original capacitor.
b) What would its value be?
C=___________
13. A milliammeter reads 35 mA full scale. It consists of a 0.40-? resistor in parallel with a40-? galvanometer.
a) How can you change this ammeter to a voltmeter giving a full-scale reading of 30 Vwithout taking the ammeter apart?
b) What is the value of this resistor?
R=______________
c) What will be the sensitivity (?/V) of your voltmeter?
sensitivity= _________ ?/V
14. Eight 7.0-W Christmas tree lights are connected in series to each other and to a 220-V source.
What is the resistance of each bulb?
R = _____________
15. What is the ratio of the voltage V1 across capacitor C1 in (Figure 1) to the voltage V2 across capacitor C2? Suppose that C2 = 1.2 ?F .
V1/V2 = _______
() Three resistors in parallel can be placed in series with the net resistance. () Two resistors in parallel can be placed in series with the third. () Two resistors in series can be placed in parallel with the third. () The resistors can all be connected in parallel. () The resistors can all be connected in series. () Two resistors in series can be placed in parallel with the net resistance. 12.0 V 22 12 12.0 V 11 16 60 W 6.0V 13Explanation / Answer
1.
Resistance of bulb 1 is 50 W ,120 V
R1=V2/P =1202/50
R1=288 ohms
Resistance of bulb 2 is 15 W,120 V
R2=1202/15 =960 ohms
Net resistance
1/Req =1/R1 + 1/R2 =1/288 + 1/960
Req=221.54 ohms
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7.
equivalent resistance of five ,560 ohms resistance in parallel is
1/Req =1/560 +1/560 + 1/560 +1/560 +1/560
Req=112 ohms
equivalent resistance in series for identical resistor is
Req=NR
=>N=Req/R =112/14 =8
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