Q:

How to dynamically append time in a file using Powershell

Hopefully I worded that title correctly.
Transcript files don't show the info I want and I need to be able to see specific events at a glance, so I am adding an additional file that I am using as a log file. 
I want to have the time appended at the beginning of each line, but it simply takes the the time it retrieved at the beginning of the script and uses that over and over again.
Script:
start-transcript -path "C:\temp\transcript  $(get-date -f dd-MM-yyyy).txt"
$log = "c:\temp\log $(get-date -f dd-MM-yyyy).txt"
$logtime = Get-Date -Format "hh:mm:ss"

Write-output "$logtime First line" | add-content $log
start-sleep -s 60
Write-output "$logtime Second line" | add-content $log

stop-transcript
exit

This is the output that I get, even though it sleeps for a full minute:
02:43:52 First line
02:43:52 Second line

There may very well be no way to do this, but thought I would give it a shot anyways. 
Thanks for any help.

A:

Can you assign this to $logtime each time you want to output it instead?
$logtime = [System.DateTime]::Now

This method promises to get current time. 
Edited to remove the suggestion that you re-assign to Get-Date each time since that didn't work for you.

