Chapter 17 Homework 37. In a lightning strike lasting 45 ms, a total charge of 3

Question

Chapter 17 Homework 37. In a lightning strike lasting 45 ms, a total charge of 350 C is transferred to the ground. What is the current during the lightning strike? 40. Find the resistance between two ends of an aluminum wire 0.25 m long and 1.0 cm in diameter. (Fo aluminum p 2.75x10 Om). 46. A 12.0 V battery produces 230 mA when connected across a so.0 load. A) What is the battery's internal resistance? B) Find the potential difference across the battery's terminals. 47, when an 18.0 V battery is connected across a 130 ? load the potential difference across the terminals is 17.4 V. What's the internal resistance? 52. A 34 ? and a 45 ? resistor are connected in series. A) Find the equivalent resistance. B) Find the current through each resistor and the voltage across each resistor when this series combination is connected across a 7.5 V battery. 53. A 250 a resistor and a 370 0 resistor are connected in parallel. A) Find the equivalent resistance. B) Find the current through each resistor and the voltage across each resistor when this series combination is connected across a 12 V battery. 57. You're given a box of 10 resistors (unlimited supply). How would you connect the resistors to make the following equivalent resistances: a) 2 ? b) 35 ? c) 7 ? d) 19 ?. 61. Three resistors, each with resistance 50 k2 are connected as shown below. What voltage should the battery have to supply a current of 1.0 mA? R1 Rs 69. A hair dryer consumes 1750 W when connected to a 120 V source. A) Find the current in the hair dryer. 8) How much energy is consumed if the hair dryer runs for 10 min? 78, A 25 nF capacitor is connected in series with a 1.45 ?? resistor, which is connected across a 24.0 V battery. The capacitor is initially uncharged. A) What is the maximum charge the capacitor will eventually attain? B) How much time does it take the capacitor to reach 90% of its maximum charged) What is the time constant for this set up?

Explanation / Answer

Remember:
For series combination
Req = R1 + R2 + R3 +...............
for parallel combination
1/Req = 1/R1 + 1/R2 + 1/R3 + ............
for 2 resistors in parallel it will be
Req = R1*R2/(R1+R2)
Remember in resistors parallel combination voltage distribution in each part will be same and in series combination current distribution in each resistor will be same.
Using this Information:

52

Req = 34 + 45 = 79 ohm

ieq = V/Req = 7.5/79 = 0.095 Amp

Since in series So

Current in 34 ohm = current in 45 ohm = 0.095 Amp

Voltage in 34 ohm = 0.095*34 = 3.23 V

Voltage in 45 ohm = 0.095*45 = 4.27 V

53

Req = 250*370/(250 + 370) = 149.2 ohm

ieq = 12/149.2 = 0.080 Amp

Since in parallel So

Voltage in 250 ohm = Voltage in 370 ohm = 12 V

Current in 250 ohm = 12/250 = 0.048 Amp

Current in 370 ohm = 12/370 = 0.032 Amp

57.

For Req = 2 ohm

Req = R/n

n = R/Req = 10/2 = 5 ohm

Connect five 10-ohm resistor in parallel

for 35 ohm

Break 35 in (30 + 5)

for series, Req = n*R, then n = 30/10 = 3

for parallel, Req = R/n, then n = 10/5 = 2

So add two 10-ohm in parallel, then three 10 ohm in series with them

for Req = 7 ohm

Break into (5 + 2)

add five 10 ohms in parallel and then two 10 ohm in parallel, then connect both parallel circuit in series

for Req = 19 ohm

break it into (10 + 5 + 2 + 2)

(one 10 ohm) in series with (two 10 ohms in parallel) in series with (five 10 ohms in parallel) in series with (five 10 ohms in parallel).

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