How did James Joule determine how much work is equivalent to

How did James Joule determine how much work is equivalent to how much heat?

attaching a team of horses to cannon-boring equipment

creating a system where he could change the heat either with work or with external heat sources    

defining one horsepower as the rate that a very strong horse does work

heating a gram of water by one degree

repeating Rumford\'s experiments but measuring the amount of heat created

Solution

The mechanical equivalent of heat was discovered by James Joule. To estimate the mechanical equivalent of heat, joule used to raise the temperature of a pound of water by one degree Fahrenheit. Hence, heating a gram of water by one degree is the correct option.