1) What is I 1 , the magnitude of the current that flows through the resistor R

Question

1)   What is I1, the magnitude of the current that flows through the resistor R1?  _____________ A

2)   What is V2, the magnitude of the voltage across  the resistor R2?    ______________V

3)    What is I2, the magnitude of the current that flows through the resistor R2?   _____________A

4)    What is RX, the value of the unknown resistor RX?        ______________ohms

5)    What is V1, the magnitude of the voltage across  the resistor R1?       ___________V

6) Multi Choice

A circuit is constructed with five resistors and a battery as shown. The battery voltage is V = 12 V. The values for the resistors are: R1 = 78 Ohms, R2 = 120 ?, R3 = 152 Ohms, and R4 = 62 Ohms. The value for RX is unknown, but it is known that I4, the current that flows through resistor R4, is zero.

Explanation / Answer

In a wheatstone bridge, the current in the middle branch is 0, hence this system behaves as a balanced wheatstone bridge.

now for a balanced wheatstone bridge,

Rx*R1=R2*R3

or R*78=120*152

or R=233.846 ohm

1)current in R1 can be found out by APPLYING KVL in the shorter loop,

E1-(R1+R3)*i=0

or i=12/(78+152)

or i=0.052 A

2)current in R2 by KVL,

I=12/(120+233.846)

=0.0339 A

so V2=I*R2

=4.068 V

3)I2 from above=0.0339 A

4)from above, Rx=233.846 ohm

5)V1=i*R1

=78*0.052

=4.056 V

6)R2*R3 has to equal to the initial value . hence R3 would be decreased by half.

(B) R3 would need to be decreased

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