Physics: Resistors and Current?

Question

Seven resistors are connected in series with a power source. If one resistor breaks:

1)The current in each resistor will:

a) increase

b) decrease

c) remain the same

2) The current through the power source will

a) increase

b) decrease

c) remain the same

Seven resistors are connected in parallel to a power source. If one resistor breaks:

1) The current in each resistor will

a) increase

b) decrease

c) remain the same

2) The current through the power source branch will

a) increase

b) decrease

c) remain the same

for #1 (series), i chose (c) because all the resistors experience the same amount of current . (however, my lab instructor said its (a))

for #2 (series) i chose (a) because R total is equal to R1+R2+R3 +.... so if one resistor breaks, the value of Rtotal decreases, I= V/Rtotal becomes less)

For #1 (parallel), lab instructor said its C and B for #2.

I don't know if im supposed to approach this kind of problem with the equations or picture of problem

Answer 1

Seven resistors are connected in series with a power source. If one resistor breaks:

I hate these poorly worded questions! how does it break? does it go open (current decreases) or does it go short (current increases) or does it just change value?

2) The current through the power source will

see above

Seven resistors are connected in parallel to a power source. If one resistor breaks:

see above. how does it break? does it go open (current decreases) or does it go short (current increases) or does it just change value?

Your instructor is an idiot!

for #1 (series), i chose (c) because all the resistors experience the same amount of current . (however, my lab instructor said its (a))

Your instructor is an idiot!

You may quote me.

Define what "break" means and i can help more.

.

Answer 2

KVL stands for KIRCHOFF'S VOLTAGE LAW

KCL stands for KIRCHOFF'S CURRENT LAW

you can get details in this link,

http://www.allaboutcircuits.com/vol_1/ch...

http://www.allaboutcircuits.com/vol_1/ch...

and CT is current tansformer.

http://www.allaboutcircuits.com/vol_2/ch...

hope this will help you.

Answer 3

for #1(series): if u mean by break, get out of circuit leaving rest of ct closed and intact, then offcourse current will increase.

for #1(parallel): the currents, in each resistor,  will remain the same as source is constant, and each resistor value is const.

for #2(parallel) it will decrease, since the summation of currents will be shortened the one which has broke.

anyway mike, listen, its tricky really tricky but there r some stuff u have to keep in mind approaching such problems:

first is kvl and kcl

this means that current will sum to zero at any given point within a ct, in=out, simple!

now another thing: V=IR (ohm's law)

this means that across any element the V will equal to the product of current passing thru that element and its resistance value.

but trust me even if its simple, its best to make an analysis based on before/after scenarios. this will be most useful and correct!