Help on an exam question

[westos-electric]

Hi

I need help working this cal. Please can you confirm the answer and how it's worked out?

Question

A conductor 500mm long is placed in at right angles to a magnetic field with a magentic flux density of 0.25 tesla. What is the current required in the conductor to create a force of 15N on the conductor.

Hope you can help
Wayne

 

[dichroic]

You may find this electrical maths pack useful.

Regards

Dichroic

 

[westos-electric]

Hi ive still had issues with this question

A small heating circuit draws 1.5kw of power and has an internal resistance of 0.5ohms what is the current drawn?

 

[Guest123]

This is an ohms law question........


Current (I) = square root of, power (P) / resistance (R)

= Sqrt of 1500 / 0.5 = 54.77A.

 

[westos-electric]

I've been reading about transformers and need help on this question

A transformer has an output of 12kva and a power factor of 0.9. the total losses in the transformer are 600w. What is the efficiency of the transformer

now i know / think the formula is output/ output power + losses

I'm not sure how this works out, can anyone help

cheers

 

[dichroic]

I've been reading about transformers and need help on this question

A transformer has an output of 12kva and a power factor of 0.9. the total losses in the transformer are 600w. What is the efficiency of the transformer

now i know / think the formula is output/ output power + losses

I'm not sure how this works out, can anyone help

cheers

The formula you require is:

input power = output power + losses

However you need to use:

Efficiency = output power / (output power + losses)

so: Output power = KVA x Power factor

12kva x 0.9 = 10.8kw

Efficiency = 10800 / (10800+600) = 0.947

0.947 x 100 = 94.7% efficient.

Regards

Dichroic