is there a flash when using the camera on the iPad?

No flash.

Unlike iPhone, there's no LED flash on iPad. But iPad's specs indicate that it does have a backside illumination sensor to increase the amount of light captured and thereby improve low-light performance. Apple say:

"The 5‑megapixel iSight camera features a backside illumination sensor that captures great-looking pictures whether by sunlight or candlelight." (Source)