It is in The Amusement Park. Firstly talk to N and go on The Ferris Wheel with him.
Then when you come off Team Plasma will be outside. Battle N and then walk to the other building with Roller Coasters and at the end Elesa (the gym leader) is waiting. She uses two Emolga's who keep using volt switch between each other and then she uses Zebstrika. They are both Electric Pokemon. Emolga is weak to Rock and Ice and Zebstrika is weak to Ground Type Pokemon. It is the Forth Gym Badge. Hope this helped ya :)!
The Nimbasa Gym is right of were the old one was (in black / white), past the Ferris wheel, look for the pokeball symbol on the building
there is none but in Nimbasa City (the city with the electric gym) You Can Find the HM Strength in one of the houses and there are alot of places you can go to like an amuesment park and stadiums and a musical
You can find a Sun Stone in Raimon/Nimbasa City (The 4th Gym City) The Sun Stone can be obtained from a person in the apartment left of the Battle Subway on the 2nd floor.
Lenora, the second gym leader, is found in her gym AKA the museum in Nacrene City.
defeat the gym leader in the city it is in then you can go to in it should be the city After driftvil
it is in amusment park
In the theme park in Nimbasa City.
The Nimbasa Gym is right of were the old one was (in black / white), past the Ferris wheel, look for the pokeball symbol on the building
The Nimbasa City Gym Leader is Elesa, who specialises in Electric type Pokemon. She uses three Pokemon. Emolga Emolga Zebstrika Zebstrika is weak to Ground Emolga is weak to Rock and Ice Hope this Helped :)
Nimbasa City is the city in Unova with the fourth gym
In Nimbasa City (city north of the desert that has the 4th gym), go into the building northwest of the Pokemon center and a NPC (Non-Player Character) will give it to you.
you have to beat the gym leader. then go to the bridge and she will show up and ask the bridge guy to lower it.
it is in nimbasa city, inside the theme park next to the ferris wheel
You need to have completed her previous gym (the Rollercoaster), then you can go into her new gym a little further right.
you have to go inside the building northwest of the Pokemon center in nimbasa city. talk to an ace trainer and he will give you the hm for strength.
SunyShore City It is the last gym, so stock up on Ground Moves or whatever. :D
Sadly, no if you are looking for exp. go to black city/white forest and battle everyone. Also, you can go to Nimbasa City and go to big stadium and small court.