Download Series Circuits Homework

Adv Physics / Gen Physics
Series Circuits Homework
ANSWERS AT END
1. Given, Battery Voltage = 6 V, R1 = 5
Ω, R2 = 10 Ω and R3 = 15 Ω, determine
the following:
a) Req (equivalent resistance)
b) I (current)
c) Voltage Drop across R1 (V1)
d) Voltage Drop across R2 (V2)
e) Voltage Drop across R3 (V3)
f) Verify that Vbattery = (V1) + (V2) + (V3)
g) Power through R1 (P1)
h) Power through R2 (P2)
i) Power through R3 (P3)
j) Power delivered by battery
k) Verify that Pbattery = (P1) + (P2) + (P3)
Homework over Series Circuits, p. 1, 2/12/2014
2. We have a 3 V battery with three resistors in series.
a) If the resistance of one of the resistors increases, how will the equivalent resistance
change?
b) What happens to the value of the current?
c) Will there be any change in the battery voltage?
3. A string of holiday lights has 20 bulbs with equal resistances connected in series. When
connected to the outlet, it draws 120 V with a current of 0.05 Amps.
a) What is the equivalent resistance of the circuit?
b) What is the resistance of each bulb?
4. Given:
V battery = 90 V
R1 = 40 Ω
R2 = 15 Ω
R3 = 60 Ω
AND V1 = 60 V
Determine:
a) Req
b) The ammeter reading in
Amps.
c) V1, V2 and V3
d) Which resistor is the hottest (i.e. greatest power)?
e) Which resistor is the coolest?
Homework over Series Circuits, p. 2, 2/12/2014
5. We have the following series circuit with three light bulbs:
Bulb 1
Bulb 2
Bulb 3
Let’s say that you have one AA battery (1.5 V). Bulb 1 is a long bulb with a resistance of 4.5 Ω.
Bulbs 2 and 3 are round bulbs with resistances of 1.5 Ω each.
a) Find the equivalent resistance
b) Find the current from the battery
c) Determine the voltage drops across each light bulb
d) Which light bulb(s) will be the brightest? The dimmest?
Homework over Series Circuits, p. 3, 2/12/2014
ANSWERS:
1.
a) Req (equivalent resistance) = 30 Ohms
b) I (current) = 0.2A
c) Voltage Drop across R1 (V1) = 1 Volt
d) Voltage Drop across R2 (V2) = 2 Volt
e) Voltage Drop across R3 (V3) = 3 Volt
f) Verify that Vbattery = (V1) + (V2) + (V3) >>> 6V = 1V + 2V +3V yes
g) Power through R1 (P1) = 0.2W
h) Power through R2 (P2) = 0.4 W
i) Power through R3 (P3) = 0.6 W
j) Power delivered by battery = 1.2 W
k) Verify that Pbattery = (P1) + (P2) + (P3) >>> 1.2 W = 0.2 W + 0.4 W + 0.6 W yes
2.
a) increase
b) decrease
3.
a) 2400 Ohms b) 120 Ohms
c) no, not theoretically
4. a) Req = 115 Ohms
b) The ammeter reading in Amps = 0.783 A
c) V1, V2 and V3 : V1 = 31.32 V
V2 = 11.745 V
V3 = 46.98 V
d) Which resistor is the hottest (i.e. greatest power)? Power through R3 = 36.78 W
e) Which resistor is the coolest? Power through R2 = 9.2 W
5. a) Find the equivalent resistance = 7.5 Ohms
b) Find the current from the battery = 0.2 A
c) Determine the voltage drops across each light bulb = V bulb 1 = 0.9 V; V bulbs 2 or 3 = 0.3 V
d) Which light bulb(s) will be the brightest? The dimmest? The brightest bulb will be bulb 1.
Bulbs 2 and 3 are dimmer. Calculate the power. Bulb 1 had a power of 0.18 W. The other two
have a power less than this (0.06 W each).
Homework over Series Circuits, p. 4, 2/12/2014