Will an 11W UVC lamp kill bacteria?
Some physical methods of sterilisation are in hospitals


Steam autoclaving
Dry heat – thermostat
White light / UV light sterilization 


where continuous UV light has poor penetration. 
UV radiation heat is absorbed by proteins and nucleic acid. 
All micro-organisms contain tehm. 
They inactivate the DNA. 
There will be electronic and photochemical reactions by


photolysis
loss of colony-forming ability
enzyme inactivation
destruction of nucleic acid. 



  If I shone a UVC lamp (11W) on something (say for example a plastic
  phone case) for an hour, would that kill off a noticeable amount of
  bacteria?


Direct answer: Not all bacteria, but some. 
UV light has poor penetration so it will not expose all bacteria. 
Most prevalent bacteria there


streptococci, 
staphylococci and 
some others. 


I estimate that the majority of the bacteria will remain because the light cannot reach each corner of the object. 
In clinics, many hours and high temperatures are used to kill bacteria. 
UV light is not efficient there. 
I think the problem is that you cannot reach each corner of the object. 
The high temperature and disinfectants can then again reach the clinical instruments throughly. 
Manual work is however still needed.

You can then take examples of bacteria. 
Search their corresponding temperature ranges. 
The survival can also be dependent on the nature of the light of the bulb. 
Each bacteria has an individual structure. 
We can manipulate the environment to make bacteria more vulnerable to the heating i.e. to change the structure of the bacteria. 
We can increase the duration of the heat exposure to make kill of the bacteria more effective.