SOLUTION: In Mr. Seeley's physics class, you have to find the total resistance (R) of a circuit with 2 resistors (r1 and r2 ) using the formuula R = r1r2 divided by r1 + r2. r1 and r2 are t

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Question 300886: In Mr. Seeley's physics class, you have to find the total resistance (R) of a circuit with 2 resistors (r1 and r2 ) using the formuula R = r1r2 divided by r1 + r2. r1 and r2 are the resistance of each resistor. Resistance is measured in ohms. A circuit thtat has a total resistance of 6 ohms has a 10-ohm resistor and an unknown resistor. Find the resistance of the unknown resistor. Please explain... I don't know where to begin this problem!!!
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In Mr. Seeley's physics class, you have to find the total resistance (R) of a circuit with 2 resistors (r1 and r2 ) using the formula R = r1r2 divided by r1 + r2. r1 and r2 are the resistance of each resistor. Resistance is measured in ohms. A circuit that has a total resistance of 6 ohms has a 10-ohm resistor and an unknown resistor. Find the resistance of the unknown resistor. Please explain..
:
Begin by writing out the formula for 2 resistors in parallel
:
Rt = total resistance
:
= Rt
In this problem
r1 = 10
r2 is unknown
Rt = 6
;
Substituting
= 6
Multiply both sides by (10+r2), results
10*r2 = 6(10 + r2)
10*r2 = 60 + 6*r2
:
Subtract 6r2 from both sides
10*r2 - 6*r2 = 60
4*r2 = 60
;
divide both sides by 4
r2 =
r2 = 15 ohms
:
:
Check solution in the formula
Rt =
Rt =
R5 = 6