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a. In physics, Ohm's law says that current through a wire, $I$, is directly proportional to voltage, $v$ , and inversely proportional to resistance,$I$ : \[I=\frac{V}{R}.\]
It's also true that resistance is directly proportional to the length of the wire. We have a piece of wire. We pass $50$ volts through this wire and measure $200$  milliamps of current. If I cut the wire in half and pass $300$ volts through it, how many milliamps of current will I measure?

 

b. All members of our painting team paint at the same rate. If $20$  members can paint a $4800$ square foot wall in $36$ minutes, then how long would it take for $9$  members to paint a $4200$ square foot wall, in minutes?

 Apr 21, 2020
edited by Guest  Apr 21, 2020
 #1
avatar+23526 
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This has been asked before

First voltage is not passed THROUGH a wire....voltage is applied ACROSS a wire   ...current goes THROUGH a wire.

 

V = IR      50 = .2 R    R = 250 ohms

Cut the wire in half  and resistance is cut in half   125 ohms

 

300v = I (125)    I = 2.4 amperes

 

 

 

b.     4800 ft2/ 20p x 36 min   = 6.6667 ft/ p -min

 

   4200 ft /      6.6667 ft2/p-min   / 9p   = 70 min

 Apr 21, 2020
edited by ElectricPavlov  Apr 21, 2020
 #2
avatar+12173 
+1

b. All members of our painting team paint at the same rate. If $20$  members can paint a $4800$ square foot wall in $36$ minutes, then how long would it take for $9$  members to paint a $4200$ square foot wall, in minutes?

laugh

 Apr 21, 2020

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