# Question regarding electric circuits and current

1. Nov 16, 2012

### 950315

1. The problem statement, all variables and given/known data

Referring to the electric circuit above, when the switch(S) turn on, the brightness bulb Q and Ammeter reading increases. so my question is, why? is it true that the S create another path way for current, then at the end of S, the electric current joins the electric current passed through bulb P , so the brightness of bulb Q increase? and why is the ammeter reading increase? Please correct me if my concept is wrong, thanks in advance.

2. Relevant equations

3. The attempt at a solution

2. Nov 16, 2012

### phinds

Do you understand how current flows in a circuit? Do you understand the relationship between resistance and current?

3. Nov 16, 2012

### 950315

As how the current flows in a circuit, I am not that certain, but for the relationship between resistance and current, I understand it with the help of ohm's law

4. Nov 16, 2012

### phinds

Good. THen how about you think of a better way of saying
and think about what that means for the current in the circuit.

5. Nov 16, 2012

### 950315

Sorry but, I don't get it..

6. Nov 16, 2012

### 950315

I just went through some reference book, and i got a conclusion. Correct me if i am wrong. The the switch S is closed, the current doesn't flow through P anymore, instead they only flow through the pathway S, as a result, the current doesn't undergo any resistance, and hence, the total Current is greater. In terms of equation, the resistance of S is negligible, so the effective resistance = 1/P + 1/0.00000000...... , and the resultant resistance is very small. Am I right?

7. Nov 17, 2012

### phinds

Yes, the bolded part is what I wanted to make sure you understand because this is what makes the total circuit resistance lower. As for specifics, I don't see any values on your diagram.

8. Nov 17, 2012

### 950315

Okay I finally got it, THANK YOU VERY MUCH DUDE !!