Books 

• NCERT Books for Class 12 Physics- Part 1
• Fundamentals of Physics Halliday and Resnick (10th Edition)

Websites

• https://ncert.nic.in/pdf/publication/sciencelaboratorymanuals/classXII/physics/lelm315.pdf  (Demonstration 7, Page no: 13).
• https://www.electronics-tutorials.ws/blog/voltmeter.html
• https://www.physicsclassroom.com/class/circuits/Lesson-4/Parallel-Circuits