In an experiment this circuit is set up. Three ammeters are used to record the currents in the three vertical branches (with
R1 ,
R2 , and
E) . The readings of the ammeters in the resistor branches (i.e. currents in
R1 and
R2 ) are 2 A and 3 A respectively.
Find the equation obtained by applying Kirchhoff’s loop rule in the loop involving
R1 and
R2 .
What will be the reading of the third ammeter (i.e. the branch with
E )? If
E were replaced by 3
E , how would this reading change?
If the original circuit is modified by adding another voltage source (as shown in the following circuit), find the readings of the three ammeters.
In this circuit, assume the currents through
R1 ,
R2 and
R3 are
I1 ,
I2 and
I3 respectively and all are flowing in the clockwise direction.
Find the equation obtained by applying Kirchhoff’s junction rule at point A.
Find the equations obtained by applying Kirchhoff’s loop rule in the upper and lower loops.
Assume
R1 =
R2 = 6 Ω,
R3 = 12 Ω,
r1 =
r2 = 0 Ω,
E1 = 6 V and
E2 = 4 V. Calculate
I1 ,
I2 and
I3 .
For the situation in which
E2 is replaced by a closed switch, repeat parts (a) and (b). Using the values for
R1 ,
R2 ,
R3 ,
r1 and
E1 from part (c) calculate the currents through the three resistors.
For the circuit in part (d) calculate the output power of the voltage source and across all the resistors. Examine if energy is conserved in the circuit.
A student implemented the circuit of part (d) in the lab and measured the current though one of the resistors as 0.19 A. According to the results calculated in part (d) identify the resistor(s). Justify any difference in measured and calculated value.
I
1 + I
3 = I
2
E
1 - I
1 R
1 - I
2 R
2 - I
1 r
1 = 0;
-E
2 + I
1 R
1 - I
3 R
3 - I
3 r
2 = 0
I
1 = 8/15 A,
I
2 = 7/15 A and
I
3 =
- 1/15 A
I
1 = 2/5 A,
I
2 = 3/5 A and
I
3 = 1/5 A
P
E1 = 18/5 W and
P
R1 = 24/25 W,
P
R2 = 54/25 W,
P
R3 = 12/25 W. Yes,
P
E1 =
P
R1 +
P
R2 +
P
R3
Kirchhoff’s rules can be used to analyze any circuit, simple or complex.
Kirchhoff’s first rule—the junction rule: The sum of all currents entering a junction must equal the sum of all currents leaving the junction.
Kirchhoff’s second rule—the loop rule: The algebraic sum of changes in potential around any closed circuit path (loop) must be zero.
The two rules are based, respectively, on the laws of conservation of charge and energy.
When calculating potential and current using Kirchhoff’s rules, a set of conventions must be followed for determining the correct signs of various terms.
The simpler series and parallel rules are special cases of Kirchhoff’s rules.
Conceptual questions
Can all of the currents going into the junction in
[link] be positive? Explain.
Apply the junction rule to junction b in
[link] . Is any new information gained by applying the junction rule at e? (In the figure, each emf is represented by script E.)
(a) What is the potential difference going from point a to point b in
[link] ? (b) What is the potential difference going from c to b? (c) From e to g? (d) From e to d?
Consider the circuit in
[link] , and suppose that the emfs are unknown and the currents are given to be
,
, and
. (a) Could you find the emfs? (b) What is wrong with the assumptions?
(a) No, you would get inconsistent equations to solve.
(b)
. The assumed currents violate the junction rule.
Wayne and Dennis like to ride the bike path from Riverside Park to the beach. Dennis’s speed is seven miles per hour faster than Wayne’s speed, so it takes Wayne 2 hours to ride to the beach while it takes Dennis 1.5 hours for the ride. Find the speed of both bikers.
from theory: distance [miles] = speed [mph] × time [hours]
info #1
speed_Dennis × 1.5 = speed_Wayne × 2
=> speed_Wayne = 0.75 × speed_Dennis (i)
info #2
speed_Dennis = speed_Wayne + 7 [mph] (ii)
use (i) in (ii) => [...]
speed_Dennis = 28 mph
speed_Wayne = 21 mph
George
Let W be Wayne's speed in miles per hour and D be Dennis's speed in miles per hour. We know that W + 7 = D and W * 2 = D * 1.5.
Substituting the first equation into the second:
W * 2 = (W + 7) * 1.5
W * 2 = W * 1.5 + 7 * 1.5
0.5 * W = 7 * 1.5
W = 7 * 3 or 21
W is 21
D = W + 7
D = 21 + 7
D = 28
Salma
Devon is 32 32 years older than his son, Milan. The sum of both their ages is 54 54. Using the variables d d and m m to represent the ages of Devon and Milan, respectively, write a system of equations to describe this situation. Enter the equations below, separated by a comma.
please why is it that the 0is in the place of ten thousand
Grace
Send the example to me here and let me see
Stephen
A meditation garden is in the shape of a right triangle, with one leg 7 feet. The length of the hypotenuse is one more than the length of one of the other legs. Find the lengths of the hypotenuse and the other leg
however, may I ask you some questions about Algarba?
Amoon
hi
Enock
what the last part of the problem mean?
Roger
The Jones family took a 15 mile canoe ride down the Indian River in three hours. After lunch, the return trip back up the river took five hours. Find the rate, in mph, of the canoe in still water and the rate of the current.
Shakir works at a computer store. His weekly pay will be either a fixed amount, $925, or $500 plus 12% of his total sales. How much should his total sales be for his variable pay option to exceed the fixed amount of $925.
I'm guessing, but it's somewhere around $4335.00 I think
Lewis
12% of sales will need to exceed 925 - 500, or 425 to exceed fixed amount option. What amount of sales does that equal? 425 ÷ (12÷100) = 3541.67. So the answer is sales greater than 3541.67.
Check:
Sales = 3542
Commission 12%=425.04
Pay = 500 + 425.04 = 925.04.
925.04 > 925.00
Munster
difference between rational and irrational numbers
Jazmine trained for 3 hours on Saturday. She ran 8 miles and then biked 24 miles. Her biking speed is 4 mph faster than her running speed. What is her running speed?