chicken6...as wot i rote, the secondary effect of use of ailerons is adverse aileron yaw.
Roll has no secondary effect, it is the motion the aircraft performs when it rotates about its longitudinal axis, whatever may cause that roll.
To demonstrate adverse aileron yaw, select reference point on the horizon, apply aileron without rudder and roll aircraft.
Aircraft nose will yaw in opposite direction to roll.
point out the effect on balance indicator.
Roll back to wings level.
Do same in opposite direction. if student hasn't yet thrown up, could continue this rolling motion to left and right. the yaw will be more evident. Also tell student to look at wing tip (should be maintaining lookout anyway).
The wing tip will magnify the effect of yaw by moving back and forward describing a oval or egg shaped passage through the air.
Rolling left, left wing tip moves forward.. rolling back to wings level, wing tip moves back.
Now repeat with co-ordinated use of rudder, show difference(Nose, wing tip, ball, stomach).
Ultimate demo, max. rate roll, collision avoidance( Watch maneouvre speed!).

BigEndBob Exactly. Nuff said.

I think that's going a bit far. There are other-axis effects for not only controls that are designed to rotate the aircraft around an axis, but also rotation about the axis itself. Roll causes both roll-damping (which tends to oppose the roll couple from the ailerons) and some yaw. The latter effect is small, because it is secondary.

Bl##dy hell! You lot have confused me - I don't know how your students cope! It's their second ever flight when they're doing this. They are only trying to get to grips with the aircraft so they can go solo after about another 10 hours or so - they haven't enrolled on a test pilot's course!

For what it's worth, the following is what I teach:

Secondary effects of controls:

Pitch - causes speed and height change - stress not realy a secondary effect in itself.

Roll - causes slip which translates to yaw which leads to a spiral dive.

Yaw - causes skid which translates to roll which leads to a spiral dive.

The above are all demos, but when demonstrating the secondary effect of roll, you teach the recovery from the ensuing spiral dive and let the student practice a recovery on the demo of the secondary effect of yaw.

Then demonstrate adverse yaw. Best done from a slow speed when induced drag is greatest and the yaw is greatest. Emphasise that it exists and he/she will have to counter it later in the course when learning turns.

I didn't invent the above - I got it from CFS. It's been good enough for them for the last 85 years, so I see no reason to change it.