Calculating Relay Resistance for 12V Circuit

AI Thread Summary
The discussion revolves around calculating the resistance of a relay in a 12V circuit where the relay activates at a current of 0.0048A. The user applies Ohm's Law, determining that the total resistance in the circuit must equal 2500 Ohms, leading to a calculated relay resistance of 1700 Ohms after accounting for the 800 Ohm resistor. There is uncertainty about whether the circuit is indeed designed to deliver the specified current of 0.0048A. Participants confirm that if the current through the coil reaches 0.0048A, the calculations are correct. The simplicity of the problem raises questions about its value in a typical homework context.
Punch
Messages
44
Reaction score
0

Homework Statement



A relay switches on when the current through the coil reaches 0.0048A.

In a circuit, a battery of 12V is connected in series with this relay it switches on when another resistor of 800 Ohm is connected to it.

Calculate the resistance of the relay.

Homework Equations





The Attempt at a Solution



V= IR
12V = 0.0048A * (800 ohm + coil resistance)

12V / 0.0048A = 800 ohm + coil resistance

coil resistance = 2500 ohm - 800 ohm
=1700 ohm

However, I am not sure if I am on the right track...
 
Last edited:
Physics news on Phys.org
Is the circuit with the battery and the resistor supposed to deliver 0.0048A? If so, your solution is right.
 
ideasrule said:
Is the circuit with the battery and the resistor supposed to deliver 0.0048A? If so, your solution is right.

from the first line, "A relay switches on when the current through the coil reaches 0.0048A."

so can i conclude that the current passing through the coil has reached 0.0048A? which means that current in the circuit is 0.0048A

however, this question is worth 4 marks and it seems to easy for a usual 4 mark question...
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Need help with a question on potential difference
Replies
7
Views
1K
Ohm's Law - Finding Source Voltage
Replies
3
Views
1K
Why do the headlights on the car become dim when the car is starting?
Replies
4
Views
2K
Electrical Circuits - Parallel vs. Series
Replies
14
Views
1K
Need some confirmation regarding induced currents
Replies
1
Views
678
How can I calculate the equivalent resistance of this circuit?
Replies
9
Views
2K
A question of electricity regarding emf and voltage
Replies
4
Views
2K
Total equivalent resistance of a combined circuit
Replies
7
Views
2K
The equivalent resistance for the resistors in this circuit?
Replies
5
Views
2K
Relay Control of Induction Motors
Replies
5
Views
720

Hot Threads

Recent Insights

Back
Top