prob set circuits

7/25/2019 Prob Set Circuits

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EEE 31 2nd Sem AY 2015-2016

Problem Set #1

1. Suppose that we want to charge up a 9 V battery and increase its energy by 500 J. How much charge must be pumpedthrough the battery? How many electrons is this? Suppose a is the positive terminal and b is the negative terminal.Should the electrons flow from a to b or b to a?

2. Suppose the average cost of residential electricity is about PhP 8.00 per kWh. If for the month of November (30 days)your bill came out to be PhP2, 880.00 and assuming a line voltage of 220V, what was the average current draw into

your house? You then realize you always left your powerful 150W desktop computer running. How much money didthat alone cost you?

3. One of the main issues about smartphones is that they need to be recharged too often. Suppose an Android smartphonerequires about 400mW to maintain a signal and data connection to the nearest tower, as well as perform regular useractivities. If the battery provides 1650mAh and a voltage of 3.7V , how long will one full charge last before the phonedies out?

4. The voltage and current at the terminals of an battery during a charge cycle are shown below.

(a) Calculate the total charge transferred to the battery.

(b) Calculate the total energy transferred to the battery.

5. Assume you are an engineer in charge of a project and one of your subordinate engineers reports that the interconnectionshown below does not pass the power check. The data for the interconnection are given in the accompanying table.

(a) Using the data given in the table, identify which components supply power. How much total power is delivered inthis circuit?

(b) Using the data given in the table, identify which components absorb power. How much total power is absorbed inthis circuit?

(c) Is your subordinate engineer correct? Explain your answer.

(d) If your subordinate engineer is correct, identify the error in the data.

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a

b c

d e f

g h

ia

+−

va

ib

+−

vb

ic

+ −

vc

ig

+−

vg

ih

+−

vh

id

+

−

vd ie

+

−

ve if

+

−

vf

Element Voltage (V) Current (A)

a 46.16 6.0b 14.16 4.72c -32.0 -6.4d 22.0 1.28e 33.6 1.68f 66.0 -0.4g 2.56 1.28h -0.4 0.4

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EEE 31 2nd Sem 2015-16 Problem Set 1 Part 2

1 Prob 2.1

Using the circuit in Fig.2.1, calculate the power absorbed by each resistor. Confirm that the netpower in the circuit is zero (i.e. total power produced = total power absorbed).

2 Prob 2.2

Using the circuit in Fig.2.2, calculate I m.

3 Prob 2.3

Using the circuit in Fig.2.3, calculate the resistance, R if the voltage across the current source is50 V. Figure out the polarity of this voltage - describe where is the higher potential (as far asthe current source is concerned).

4 Prob 2.4

Using the circuit in Fig.2.4, if the voltage source produces 5 W of power, and V x is 4 V, calculatethe resistance, R and the Gain, G.

5 Prob 2.5

Using the circuit in Fig.2.5, calculate the values of the three resistances, Ra, Rb, and Rc. Confirmthat the net power in the circuit is zero (i.e. total power produced = total power absorbed).

Reference

Dorf & Svoboda, Introduction to Electric Circuits, 9th ed. Wiley, 2014

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