series circuits




1).
When a fourth resistor is connected in series with three resistors, the total resistance
A   increases by one-fourth   
B   increases   
C   decreases   
D   remains the same   
ANS: B - increases

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2).
A string of five series resistors is connected across a 6 V battery. Zero voltage is measured across all resistors except R3. The voltage across R3 is
A   0 V   
B   1.2 V   
C   6 V   
D   0.6 V   
ANS: C - 6 V

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3).
A series circuit consists of three resistors with values of 120 , 270 , and 330 . The total resistance is
A   less than 120    
B   the average of the values   
C   720    
D   120    
ANS: C - 720 

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4).
A certain series circuit consists of a 1/8 W resistor, a 1/4 W resistor, and a 1/2 W resistor. The total resistance is 1200 . If each resistor is operating in the circuit at its maximum power dissipation, total current flow is
A   27 mA   
B   2.7 mA   
C   19 mA   
D   190 mA   
ANS: A - 27 mA

Total P = P1 + P2 + P3 = 7/8w. 

P = I2R. 

I = sqrt (P/R)

Now, P = 7/8w, R = 1200 ohm.

Therefore,

I= sqrt ( (7/8)/1200 ) = 0.0270030862 = 27 mA.

5).
Which of the following series combinations dissipates the most power when connected across a 120 V source?
A   one 220  resistor   
B   two 220  resistors   
C   three 220  resistors   
D   four 220  resistors   
ANS: A - one 220  resistor

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6).
When one of three series resistors is removed from a circuit and the circuit is reconnected, the current
A   increases   
B   ncreases by one-third   
C   decreases by one-third   
D   decreases by the amount of current through the removed resistor   
ANS: A - increases

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7).
The total power in a certain circuit is 12 W. Each of the four equal-value series resistors making up the circuit dissipates
A   12 W   
B   48 W   
C   3 W   
D   8 W   
ANS: C - 3 W

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8).
The following resistors (one each) are connected in a series circuit: 470 , 680 , 1 k, and 1.2 k. The voltage source is 20 V. Current through the 680  resistor is approximately
A   60 mA   
B   30 mA   
C   6 mA   
D   300 mA   
ANS: B - 30 mA

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9).
A series circuit consists of a 4.7 k, a 12 k, and a 2.2 k resistor. The resistor that has the most voltage drop is
A   the 12 k   
B    the 2.2 k   
C   the 4.7 k   
D   impossible to determine from the given information   
ANS: A - the 12 k

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10).
All the voltage drops and the source voltage added together in a series circuit is equal to
A  
the total of the voltage drops
  
B   the source voltage   
C   zero   
D   the total of the source voltage and the voltage drops   
ANS: C - zero

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