resistors in parallel

[NWDS]

Afternoon fellas 7 ladies, Iam struggling with the above, I have the elec calcs ( vol 1 7th ed ) and I cannt seem to get the figures for the answers I get very near but not an exact match, any help would be appreciated.

regards Iain

 

[a1]

Give an example of what you are struggling with OP.

 

[NWDS]

Afternoon fellas 7 ladies, Iam struggling with the above, I have the elec calcs ( vol 1 7th ed ) and I cannt seem to get the figures for the answers I get very near but not an exact match, any help would be appreciated.regards Iain

can you work out

1 at 4 ohms

1 at 6 ohms

1 at 9 ohms

connected in parallel what is the equivelant resistance ?? make the answers correct to 3 significant figs.

 

[a1]

RT = 1/4Ω + 1/6Ω + 1/9Ω = 1/RTΩ

RT = 0.25Ω + 0.166Ω + 0.111Ω = 1/1.021Ω = 0.979Ω

Is that what you are looking for?

 

[NWDS]

no the book says 1.89 ohms

I got

1 at 0.25

1 at 0.16

1 at 0.11

added up = 0.52

1 divided by 0.52 = 1.92 ohms

 

[NWDS]

Some of the answers in the book I get and some I donnt, I use the same formula all the time this is what is throwing me !!!!!!!!!!!.

thanks Iain

 

[a1]

The answer is 1.89Ω

 

[a1]

The clue is in the "Significant figs"

So it will be:

0.25Ω + 0.17Ω + 0.11Ω = 0.53Ω = 1/0.53 = 1.886 1.88679245283019

Rounded is 1.89Ω

 

[Voltimax]

Admin originally made a mistake with his 1/6.

He's crafty and changed it, but I saw it before he did

 

[NWDS]

0.25+0.166+0.111 = 0.527

1 divided by 0.527 is 1.89

I think that is how it should be ( I was only using 0.16 & 0.11 )

regards Iain

 

[a1]

See My Post #8

 

[NWDS]

Thanks fellas, that is the benefit of this site.

regards Iain

 

[Voltimax]

You guys post too quickly for me.

 

[ABC Technical]

This site is full of awesome people.

 

[a1]

This site is full of awesome people.

:x

 

[SPECIAL LOCATION]

can you work out 1 at 4 ohms

1 at 6 ohms

1 at 9 ohms

connected in parallel what is the equivelant resistance ?? make the answers correct to 3 significant figs.

The other way you can check Parallel resistors is use the "Product" over "Sum" method.

e.g.

two resistors R1 & R2 in parallel.

res = (R1 x R2)/(R1 + R2).

with 3 resistors you can calc two of them first then Calc third afterwards..

i.e.

4 & 6 in parallel is (4x6)/(4+6) = 24/10 = 2.4

now do

2.4 & 9 in parallel is (2.4x9)/(2.4+9) = 21.6/11.4 = 1.89473 etc.. =1.89

which proves you have your calc correct using the other 1/R1 + 1/R2 + 1/R3 = 1/Rx method.

 

[kme]

The way I would do it too, SL.

 

[extension15]

This site is full of awesome people.

That's a nice comment, I like to think we ALL contribute here..

Kev

 

[The Godfather]

That's a nice comment, I like to think we ALL contribute here..Kev

The Don is pleased.

The Godfather