The revs will rise, but the car doesn't accelerate in relation to how the revs rise. So if you floor it in a low gear i.e. putting a lot of torque through the gearbox, the revs will rise but the car won't accelerate as much as that amount of throttle should make it.
The revs rise, and will then come back down to normal when the clutch stops slipping.
VERY poor explanation, but my mind is full of uni dissertation at the moment, and so is working like a mushroom !!
