Transformar-se em um trouxa (usando Poção Polissuco) não remove magia.
Harry finge ser um garoto trouxa ruivo no casamento de Fleur e Bill.
Harry was rather uncomfortable. The Muggle boy whose appearance he was affecting was slightly fatter than him, and his dress robes felt hot and tight in the full glare of a summer’s day.
Harry Potter and the Deathly Hallows - Chapter Eight: The Wedding
Poucos minutos após o casamento ter caído (e, presumivelmente, enquanto ele ainda está transformado), ele desenha sua varinha e usa magia.
The force of the Death Eaters’ spells shattered the tiled wall where Ron’s head had just been, as Harry, still invisible, yelled, ‘Stupefy!’
The great, blond Death Eater was hit in the face by a jet of red light: he slumped sideways, unconscious.Harry Potter and the Deathly Hallows - Chapter Nine: A Place to Hide
Uma situação semelhante ocorre mais tarde no mesmo livro. Tanto Harry quanto Hermione se transformam em trouxas
They were to Apparate to the village under cover of darkness, so it was late afternoon when they finally swallowed Polyjuice Potion, Harry transforming into a balding, middle-aged Muggle man, Hermione into his small and rather mousy wife.
Harry Potter and the Deathly Hallows - Chapter Sixteen: Godric’s Hollow
alguns minutos depois, Harry usa magia para limpar algumas das fotos na casa de Bathilda Bagshot
He saw a few tiny movements from the pictures. As Bathilda fumbled with logs for the fire, he muttered, ‘Tergeo.’ The dust vanished from the photographs, and he saw at once that half a dozen were missing from the largest and most ornate frames. He wondered whether Bathilda or somebody else had removed them. Then the sight of a photograph near the back of the collection caught his eye, and he snatched it up.
Harry Potter and the Deathly Hallows - Chapter Sixteen: Godric’s Hollow
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‘Lumos,’ said Harry, and his wand ignited. He gave a start: Bathilda had moved close to him in those few seconds of darkness, and he had not heard her approach.
Harry Potter and the Deathly Hallows - Chapter Sixteen: Godric’s Hollow
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The snake lunged as he took a running leap, dragging Hermione with him; as it struck, Hermione screamed, ‘Confringo!’ and her spell flew around the room, wardrobe mirror and ricocheting back at them, bouncing from floor to ceiling
Harry Potter and the Deathly Hallows - Chapter Sixteen: Godric’s Hollow