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The rather simple circuit shown below is known as a voltage divider. The symbol consisting of three horizontal lines is represents “ground” and can be defined as the point where the potential is zero. The voltage divider is widely used in circuits and a single voltage source can be used to provide reduced voltage to a load resistor as shown in the second part of the figure. (a) What is the output voltage V out of circuit (a) in terms of R 1 , R 2 , and V in ? (b) What is the output voltage V out of circuit (b) in terms of R 1 , R 2 , R L , and V in ?

Part a shows positive terminal of voltage source V subscript in connected in series to resistors R subscript 1 and R subscript 2. The negative terminal of the source is grounded and V subscript out is between the two resistors. Part b shows the same circuit as part a but with V subscript out connected to ground through resistor R subscript L.
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Three 300 - Ω resistors are connect in series with an AAA battery with a rating of 3 AmpHours. (a) How long can the battery supply the resistors with power? (b) If the resistors are connected in parallel, how long can the battery last?

a. t = 3 A · h 1.5 V 900 Ω = 1800 h ; b. t = 3 A · h 1.5 V 100 Ω = 200 h

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Consider a circuit that consists of a real battery with an emf ε and an internal resistance of r connected to a variable resistor R . (a) In order for the terminal voltage of the battery to be equal to the emf of the battery, what should the resistance of the variable resistor be adjusted to? (b) In order to get the maximum current from the battery, what should the resistance variable resistor be adjusted to? (c) In order for the maximum power output of the battery to be reached, what should the resistance of the variable resistor be set to?

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Consider the circuit shown below. What is the energy stored in each capacitor after the switch has been closed for a very long time?

The positive terminal of voltage source V of 12 V is connected to an open switch. The other end of the open switch is connected to resistor R subscript 1 of 100 Ω which is connected to two parallel branches. The first branch has capacitor C subscript 1 of 10 mF and R subscript 2 of 100 Ω. The second branch has R subscript 3 of 100 Ω and C subscript 2 of 4.7 mF.

U 1 = C 1 V 1 2 = 0.16 J , U 2 = C 2 V 2 2 = 0.075 J

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Consider a circuit consisting of a battery with an emf ε and an internal resistance of r connected in series with a resistor R and a capacitor C . Show that the total energy supplied by the battery while charging the battery is equal to ε 2 C .

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Consider the circuit shown below. The terminal voltages of the batteries are shown. (a) Find the equivalent resistance of the circuit and the current out of the battery. (b) Find the current through each resistor. (c) Find the potential drop across each resistor. (d) Find the power dissipated by each resistor. (e) Find the total power supplied by the batteries.

The figure shows two series voltage sources of 12 V each with upward negative terminals connected to four resistors. The sources are connected in series to resistor R subscript 1 of 14 Ω connected in series to two parallel resistors, R subscript 2 of 9 Ω and R subscript 3 of 18 Ω connected in series to resistor R subscript 4 of 4 Ω.

a. R eq = 24.00 Ω ; b. I 1 = 1.00 A , I 2 = 0.67 A , I 3 = 0.33 A , I 4 = 1.00 A ;
c. V 1 = 14.00 V , V 2 = 6.00 V , V 3 = 6.00 V , V 4 = 4.00 V ;
d. P 1 = 14.00 W , P 2 = 4.04 W , P 3 = 1.96 W , P 4 = 4.00 W ; e. P = 24.00 W

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Consider the circuit shown below. (a) What is the terminal voltage of the battery? (b) What is the potential drop across resistor R 2 ?

The negative terminal of voltage source V is connected to two parallel branches, one with resistor R subscript 1 of 40 Ω with downward current I subscript 1 of 50 mA and second with R subscript 2 of 5 Ω in series with R subscript 3 of 15 Ω.
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Consider the circuit shown below. (a)Determine the equivalent resistance and the current from the battery with switch S 1 open. (b) Determine the equivalent resistance and the current from the battery with switch S 1 closed.

The negative terminal of voltage source of 12 V is connected to two parallel branches, one with resistor R subscript 1 of 8 Ω in series with resistor R subscript 4 of 8 Ω and second with R subscript 2 of 8 Ω in series with R subscript 3 of 8 Ω. The branches are connected together to resistor R subscript 5 of 4 Ω. An open switch S connects the two branches in the middle.

a. R eq = 12.00 Ω , I = 1.00 A ; b. R eq = 12.00 Ω , I = 1.00 A

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Two resistors, one having a resistance of 145 Ω , are connected in parallel to produce a total resistance of 150 Ω . (a) What is the value of the second resistance? (b) What is unreasonable about this result? (c) Which assumptions are unreasonable or inconsistent?

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Two resistors, one having a resistance of 900 k Ω , are connected in series to produce a total resistance of 0.500 M Ω . (a) What is the value of the second resistance? (b) What is unreasonable about this result? (c) Which assumptions are unreasonable or inconsistent?

a. −400 k Ω ; b. You cannot have negative resistance. c. The assumption that R eq < R 1 is unreasonable. Series resistance is always greater than any of the individual resistances.

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Practice Key Terms 3

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Source:  OpenStax, University physics volume 2. OpenStax CNX. Oct 06, 2016 Download for free at http://cnx.org/content/col12074/1.3
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