E (Electromotive Force/Volts) = I (current/amperes) x R (resistance/ohms)
Items wired in series share voltage.
Items wired in parallel (your case) share amperage.
One needs to know the amperage draw of each item being plugged in and then add them up to determine if the circuit can handle them. Probably need to look at the fuse for the circuit.
In all things electrical
, amperage is the bad boy. Amperage yields power quickly
P (power) = I ^2^ (amperage squared) x E (voltage)
Notice that in the power equation the amperage factor is squared. This leads into difficulties very quickly.
Voltage is best explained by walking across a carpet and then touching something grounded. That shock you get could be a couple thousand volts, but the amperage is so low, micro or mini amps so that no harm is done.