Question

Circuit Two

A 60 ohm resistor is in branch 3, a 20 ohm resistor in branch 2 and a 10 ohm resistor in branch 1.

All resistors are connected in parallel with a 90V battery.

Calculate the equivalent resistance of the circuit.

How many current paths are there in this circuit?

What should the current be in the equivalent circuit? Remember I _eq = V_eq/R_eq.

Now discuss whether or not the junction rule has been satisfied. Use your data to support your answer.

Now discuss whether or not the loop rule has been satisfied. Use your data to support your answer.

Resistance (?)	Current (include units)	Voltage ( include units)
60	15 A	9 V
30	30 A	9 V
10	90 A	9 V
Total

Answer 1

(a) Since resistance are in parallel    1/Rp = 1/R1 + 1/R2 + 1/R3                     (R1= 10 , R2= 20, R3= 60 ohm)

Rp= 6 ohm

(b) There are three paths of currents I1, I1,I3 as shown in fig.

(c) I_eq = V_eq/ R_eq = 90/6 = 15 A

(d) Junction rule :

incoming current= outgoing current ie I= I1+I2+I3

I1= V/R1 =9A,    I2= V/R2 = 4.5A , I3= V/R3= 1.5 A,      I= 15 A

15= 9+4.5+1.5= 15           HENCE JUNCTION RULE SATISFIED

BY APPLYING LOOP RULE    -E+IR =0

E= IR

90V= 15* 6= 90    hence loop rule is satisfied