[Wolves] Much difference between 4.5v and 5v?

[Mark Ellse]

Now listen chaps, sorry to be too much of a physics teacher about this 
voltage and current lark, but here is what is really necessary.

There are three important things about a power supply:

1   That it provides the right voltage. For most operations, the exact 
voltage is not important and plus or minus 10% is fine. (Even 
old-fashioned TTL 5V logic could cope with 10% either way.) In the case 
under discussion, the difference between 4.5 V and 5 V is not important.

2   That the supply gives the right type of voltage. The vast majority 
of plug-top power supplies give a smoothed and unregulated output. So 
the voltage is usually very high off load, but drops a lot when the load 
is connected. A typical 5V unregulated power supply may be as high as 9V 
off load. Very occasionally an odd piece of kit requires a regulated 
supply. If you get the better quality plug-top power supplies, they will 
give a regulated output.

3   That the power supply gives ENOUGH current. The current rating of a 
power supply gives the maximum current it can deliver. The appliance 
connected to it will only draw as much current as it needs. So if a 
device needing 300 mA is connected to a supply rated at 2.5 A, then 
things will be fine, becuase the device will only take the 300 mA that 
it needs, and the power supply will be happy.
On the other hand, if this router needs 2.5A and the power supply is 
rated at 300 mA, then the power supply will simply not deliver enough 
current to power it.

Further information on the above in Electricity and Thermal Physics by 
Ellse and Honeywill, published by Nelson Thornes and available from Amazon.

If you read this far and are grateful for the electrical illumination, 
in return tell me how the Red Hat/Fedora menue structure works and how 
to add and delete things from the Start menu.

Cheers,

Mark