770 views

### A lamp has a rating of 18V 9W. How much energy is transferred to the bulb in 5 minutes? Calculate the current through it when connected to a 18V supply.

The first question comes from the realisation that the power rating, "9W" represents 9 joules being supplied every second and so can be written as 9J/s and so in 5 minutes (or 300 seconds) the energy supplied is:
9J/s * 300s = 2700J

The second part comes from the equation P=IV and we already have numbers for power and voltage:
9 = 18 * I
I = 9/18 = 0.5Amps

2 years ago

Answered by Alexander, a GCSE Physics tutor with MyTutor

## Still stuck? Get one-to-one help from a personally interviewed subject specialist

#### 218 SUBJECT SPECIALISTS

£36 /hr

Degree: Medicine (PhD) (Doctorate) - Bristol University

Subjects offered:Physics, Science+ 5 more

Physics
Science
Geology
Extended Project Qualification
Chemistry
Biology
-Personal Statements-

“I have been teaching here since 2013 and use various teaching styles depending on what helps you to learn best!”

£36 /hr

Degree: Architecture and Environmental Engineering (Masters) - Nottingham University

Subjects offered:Physics, Maths+ 2 more

Physics
Maths
Design & Technology
-Personal Statements-

“Hi there, I have a passion for helping students achieve, and believe that with my 200+ hours of experience, we will be able to surpass the grades you want!”

£30 /hr

Degree: Physics (Masters) - Durham University

Subjects offered:Physics, Music+ 4 more

Physics
Music
Maths
Further Mathematics
Chemistry
-Personal Statements-

“Hello everyone! My name is Anuradha (you can call me Anu), and I am a Physics Undergrad at Durham. I have always had a “thing” for science and am so pleased to be studying it – and hope that I can give you all the support you need to ...”

Currently unavailable: for regular students

Degree: Physics (Bachelors) - Durham University

Subjects offered:Physics

Physics

“About me:I am a physics student, studying at Durham University and I have always loved teaching people. I initially started it as my favourite way to learn and study. I would try to teach anything I had learnt to a friend, my parents...”

MyTutor guarantee

### You may also like...

#### Posts by Alexander

A lamp has a rating of 18V 9W. How much energy is transferred to the bulb in 5 minutes? Calculate the current through it when connected to a 18V supply.

On a see-saw Mary, weight 600N balances John, weight 200N when she sits 1.5m away from the pivot. How far from the pivot is John?

Resistors of 5 ohms and 10 ohms are connected in series with a battery supplying 3 volts. What is the total resistance ? And calculate the current in the circuit.

The loudspeaker produces a sound wave with a frequency of 850 hertz and a wavelength of 0.4 metres. Calculate the speed of this sound wave. Give the unit

#### Other GCSE Physics questions

Explain why the National Grid includes step-up transformers.

What is an isotope?

How can an object be at rest without friction?

What is the Doppler effect?

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this.