RiahDawson
Badges: 17
Rep:
?
#1
Report Thread starter 4 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
reply
RiahDawson
Badges: 17
Rep:
?
#2
Report Thread starter 4 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
reply
RiahDawson
Badges: 17
Rep:
?
#3
Report Thread starter 4 years ago
#3
Bump.
0
reply
RiahDawson
Badges: 17
Rep:
?
#4
Report Thread starter 4 years ago
#4
Physics
0
reply
RiahDawson
Badges: 17
Rep:
?
#5
Report Thread starter 4 years ago
#5
...
0
reply
RiahDawson
Badges: 17
Rep:
?
#6
Report Thread starter 4 years ago
#6
Physics
0
reply
RiahDawson
Badges: 17
Rep:
?
#7
Report Thread starter 4 years ago
#7
Heeh
0
reply
Joinedup
Badges: 20
Rep:
?
#8
Report 4 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
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

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

Personalise

University open days

  • Sheffield Hallam University
    Get into Teaching in South Yorkshire Undergraduate
    Wed, 26 Feb '20
  • The University of Law
    Solicitor Series: Assessing Trainee Skills – LPC, GDL and MA Law - London Moorgate campus Postgraduate
    Wed, 26 Feb '20
  • University of East Anglia
    PGCE Open day Postgraduate
    Sat, 29 Feb '20

People at uni: do initiations (like heavy drinking) put you off joining sports societies?

Yes (534)
66.5%
No (269)
33.5%

Watched Threads

View All