ChipolaJunior College - Spring 2004

PHY 1054 - Exam III

  1. Consider the combination of resistors and voltage sources shown in the circuit drawn below. Be sure to specify the direction of each current in answering the questions below.

a)Calculate all of the individual currents flowing through the circuit branches.

b)What is the potential difference measured across the 707  resistor?

c)Find the power provided to the circuit by each individual battery.

d)How much power is dissipated in the 332  resistor?

e)The 175 V battery shown in the circuit is composed of 175 V EMF and internal resistance of 0.35 (because of the small resistance, the currents flowing in the circuit do not change much from part a). Calculate the terminal voltage of the battery; do not round your answer.

  1. The network of resistors shown below is connected across an ideal battery with an EMF equal to 900 V.

a)Find the equivalent resistance for this combination.

b)Calculate the current drawn from the battery?

c)How much power does the battery provide in the circuit?

d)Calculate the potential difference across the 187  resistor.

e)How much power is dissipated in the 187  resistor?

  1. A common light bulb is constructed by connecting the ends of an 11.3 m length of high resistance wire to the bulb socket. The thin filament wire has a circular cross section with radius 0.000078 m. Further, the metal wire from which the filament was made has a resistivity of 9.8x10-6m measured at 20 oC, and a temperature coefficient of 8.6x10-3oC-1. Answer the following questions for the resistor described above.

a)What is the resistance of the light bulb if the filament heats up to 2500 oC when connected across a potential difference of 110V?

b)How much power is dissipated in the light filament when connected to the 110 V voltage source?

c)Calculate the current through the light bulb when connected to the 110 V power supply?

d)When the light bulb is connected to a 220 V battery, it heats up such that a current of 16 A flows through the circuit. Calculate the resistivity of the metal for this situation

e) How much power is used by the light bulb when connected as described in part d).

I = Q/t

V = IR

R = L/A

= o(1+T)

P = IV = V2/R = I2R

REQ = R1+R2+R3+…

1/REQ = 1/R1+1/R2+1/R3+…

Iin =Iout

closed loopV = 0