my cat take a wizz on the carpet?

This is an unnatural act for a cat.  They have a strong instinct to pee in spots where it won't be detected, so as long as you provide clean litter, they will prefer that.  But if the litterbox isn't clean, they will go elsewhere.  And 'how clean' a box has to be varies from cat to cat.

The other main reason for a cat going outside the box will be stress.  If a cat is stressed for some reason, it may pee elsewhere for reasons ranging from territory marking to fear of other animals to fear of people or just being upset.  Try to calm your cat.  There are pheremone sprays you can put down to chill your cat.  Talk to your vet for ideas.  There are also medical conditions that can cause this.

The bad news is that once peeing outside the box starts, it's liklihood to repeat in the future is MUCH higher.  Clean the area thoroughly, though likely the cat will still smell it.  But the stronger the odor, the greater the signal to the cat that this is an area to go again in the future.  I recommend one of those portable carpet shampoo thingies like the Bissell SpotBot.  Or is it Hoover?  Whichever, the SpotBot is pretty good (though it wears down due to cheap plastic parts and needs replacing every so often).

Your cat very likely has a urinary tract infection (UTI).  This can kill him if not treated.  Get him in to your vet quickly.

That's not normal for a cat. Make sure your cat's litter box is clean as cats don't like dirty litter boxes, and take him to the vet to make sure he doesn't have a UTI, so he can get treated if he does. Also if he doesn't like the type of litter, try changing it. And make sure to clean your carpet using one of those pet odour cleaners 

Cats pee on the carpet because they're trying to tell you something. It could be caused by a number of things;  first, cats like a clean litterbox, so you have to scoop out the litter daily.  If it's too messy the cat will sometimes pee on the floor.  The other thing it could be, is a possible infection which is common in older cats.  Last, it could be that your cat is showing he's unhappy, with his environment, or perhaps other cats or pets in the house.  Be sure to clean the carpet as soon as possible, with a carpet cleaner specifically for pet stains and odors.  Definitely take your cat to the vet if he keeps going in the carpet because he could have a health problem.