# End and internal resistance help

Thread starter 6 years ago
#1
Completely don't understand what I'm doing in question 2,3,4. Help appreciated.
2. A typical car battery has met 12V, must provide current 80A to starter mother.
A) why must it have v. Love resistance?
B) if internal resistance 0.05ohms find p.d. Across internal resistance when motor is running.
C)

3. 3000V power pack, with 50Mohms resistor not series
A) maximum current that can be drawn?
B) purpose of 50MOhms resistor?
C) why must resistor be in connected in series with supply?
0
Thread starter 6 years ago
#2
4. High resistance voltmeter reads 20V across terminals of d.c power supply. High resistance metre is disconnected and sencond voltmeter with resistance of 1.0k is connected across supply. Second metre is 16V.
A) emf of power supply?
B) calculate current flowing through second metre
C) calculate internal resistance of power supply
D) show current is equal to 0.08A when supply is short circuited
0
Thread starter 6 years ago
#3
Bump.
0
Thread starter 6 years ago
#4
Physics
0
Thread starter 6 years ago
#5
...
0
Thread starter 6 years ago
#6
Physics
0
Thread starter 6 years ago
#7
Heeh
0
6 years ago
#8
2.a. Power developed by resistance=I2R
if the battery is supplying 80A you can calculate the power developed by (for example) a 1 ohm internal resistance, which is power going into raising the temperature of the battery. for comparison a 1 bar electric fire is 1000 watts.

2.b. Ohms law V=IR

3.a Ohms law again
3.b & c - well they put resistors in there to limit the maximum current to non-lethal levels

4. Ohms law again.
1
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### Y13's - If you haven't confirmed your firm and insurance choices yet, why is that?

I am waiting until the deadline in case anything in my life changes (5)
17.24%
I am waiting until the deadline in case something else changes (e.g. exams/pandemic related concerns) (3)
10.34%
I am waiting until I can see the unis in person (4)
13.79%
I still have more questions before I make my decision (3)
10.34%
No reason, just haven't entered it yet (7)
24.14%
Something else (let us know in the thread!) (7)
24.14%

View All
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.