Western blot
Then the scientist turns on the electrodes to make a charge.  This can be 60V. The proteins have a negative charge, so they move toward the positive side of the gel as if they are running a race.  The scientist or technician waits for some time.  This can be 90 minutes.  Then the scientist turns off the electrodes so that the proteins stop moving.  Then they look at the gel to see how far each sample moved.  Small proteins move through gel faster than large proteins, so they move further.  Proteins with big electric charges move faster than proteins with small electric charges.  These are some of the ways a Western blot helps scientists tell proteins apart.