Replace Residential Circuit Breaker and Verify Connections

What happens here

The electrician proceeds to replace the faulty 15-amp single-pole circuit breaker. He retrieves a new Cutler Hammer circuit breaker from his service van. He installs the new breaker and ensures that the circuit breaker terminals are tightened down securely to prevent any future loose connections. After replacement, he checks the voltage in the electrical panel to confirm 240 volts between the hot legs and 120 volts from a hot leg to the neutral, verifying proper power supply.

Goal: Replace the faulty circuit breaker and ensure all electrical connections are secure and voltage is correct.