first, did you get my pm? id really like some help :P
and in answer to your question:
a systematic error is where all of your results are shifted from the true value due to a consistent error. In your experiment your ammeter/voltmeter may not have read zero at the start (which you should have checked by attaching the voltmeter to itself) which would have caused all of your results to be a bit out. also you could have made a consistent error in technique which may have been poor technique in reading the length of the wire.
A random error is caused by poor technique/faulty instruments/human error leading to a few measurements being wrong, creating anomalies. this could happen if you sometimes read the length of the wire wrong/rounded it wrong or if you didnt keep variables the same,the wire may have gained in temperature.