Alpha particles are positively charged, beta particles are negatively charged and gamma radiation is electrically neutral. This means that alpha radiation and beta radiation can be deflected by electric fields, but gamma radiation is not deflected.
Because they consist of charged particles, alpha radiation and beta radiation can also be deflected by magnetic fields. Just as with electric fields, gamma radiation is not deflected by magnetic fields.
[ This page has been adapted from www.bbc.co.uk/schools/gcsebitesize/science