# Alternating Current Circuits and Electromagnetic Waves

#### ScoutFCM

Just wanted to know if someone could help me out or check my answers.

The Transformer
38) A step-down transformer is used for recharging the batteries of portable devices such as tape players. The turns ratio inside the transformer is 13:1 and it is used with 120V (rms) household service. If a particular ideal transformer draws 0.350A from the house outlet, what are (a) the voltage and (b) the current supplied to a tape player from the transformer? (c) How much power is delivered?

a) ∆V= -N(∆Ф)/∆t = ???
I don't know how to get current/number of turns.

b) Ф= V∆t/-N ?

c) (.350A)(120V) = 42W

Related Introductory Physics Homework Help News on Phys.org

#### Doc Al

Mentor
properties of an ideal transformer

You need to understand two things about an ideal transformer:
(1) The ratio of the voltages (primary to secondary) equals the ratio of the number of turns. (This comes from Faraday's law.)
(2) The power in the primary equals the power in the secondary (from energy conservation):
$$V_pI_p = V_sI_s$$

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving