what are the causes for high CPU usage?

[Carl Patrick]

what factors could possibly cause a cpu to have a high usage? is it purely up to the tasks running at the current time or can other factors of the cpu change this such as clock speed or temperature?
honestly it's quite a basic question yet there are no easy to find answers as far as i can see.

 

[WildCard999]

Malware can cause high CPU usage.

 

[rgd1101]

the cause is more app is using the cpu.

 

[Ilijas Ramic]

Windows ? Cpu? go to resource monitor and see what process chugs the cpu usage